Acronis OS SELECTOR 8.0 User Manual
User's Guide
OS Selector 8.0
Compute with confidence
www.acronis.com
Copyright © SWsoft, 2000-2002. All rights reserved.
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Copyright © SWsoft, 2000-2002 3
ENTIRE RISK
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4
Table of Contents
ABOUT THIS GUIDE ............................................................................................ 9
CHAPTER 1. INTRODUCTION ......................................................................... 11
1.1 ACRONIS OS SELECTOR AS A BOOT MANAGER............................11
1.2 ACRONIS OS SELECTOR AS A PARTITION MANAGER.................... 12
1.3 ACRONIS OS SELECTOR KEY FEATURES ...................................... 12
1.4 MAIN DISK ADMINISTRATOR FEATURES....................................... 13
1.5 ACRONIS OS SELECTOR SYSTEM REQUIREMENTS........................ 14
1.6 HOW DOES ACRONIS OS SELECTOR FUNCTION? .......................... 15
1.7 WHAT IS A BOOT CONTEXT?......................................................... 15
CHAPTER 2. BASIC INFORMATION................................................................ 17
2.1 WHAT IS A HARD DISK? ................................................................ 17
2.1.1 HARD DISK ARCHITECTURE ..................................................................... 17
2.1.2 HOW DOES HARD DISK WORK?................................................................ 17
2.2 HARD DISK FORMATTING ............................................................. 18
2.2.1 PHYSICAL FORMATTING ...........................................................................18
2.2.2 LOGICAL FORMATTING ............................................................................. 18
2.3 FILE SYSTEMS................................................................................ 19
2.3.1 FAT16...................................................................................................... 19
2.3.2 FAT32...................................................................................................... 20
2.3.3 NTFS........................................................................................................20
2.3.4 LINUX EXT2 .............................................................................................20
2.3.5 LINUX EXT3 .............................................................................................21
2.3.6 LINUX REISERFS ......................................................................................21
2.4 PARTITIONS ................................................................................... 21
2.4.1 WHEN IS IT USEFUL TO HAVE MULTIPLE PARTITIONS? ............................21
2.4.2 PARTITION STRUCTURE ON A HARD DISK ................................................. 21
2.5 BOOT SEQUENCE ........................................................................... 23
2.5.1 VERY BEGINNING .....................................................................................23
2.5.2 BOOTING WITHOUT THE BOOT MANAGER ................................................ 23
2.5.3 WHAT DOES THE BOOT MANAGER DO? ....................................................23
2.6 MANAGING PARTITIONS................................................................ 24
2.6.1 SETTING AN ACTIVE PARTITION ...............................................................24
2.6.2 ACCESSING THE SAME FILES FROM MULTIPLE OPERATING SYSTEMS ......24
2.6.3 EFFICIENCY OF DISK SPACE USAGE..........................................................24
2.7 HIDDEN PARTITIONS ..................................................................... 25
2.8 DRIVE LETTERS .............................................................................26
2.9 ASSIGNMENT OF LETTERS IN DIFFERENT OPERATING SYSTEMS .. 26
2.9.1 MS-DOS 5.0-6.22, MS-DOS 7.0, WINDOWS 95 (ORIGINAL) ...................26
2.9.2 MS-DOS 7.1/8.0, WINDOWS 95 OSR2/98/ME ........................................ 27
2.9.3 OS/2 .........................................................................................................27
2.9.4 WINDOWS NT/2000/XP............................................................................27
2.10 TROUBLES ARISING FROM CHANGING LETTER ASSIGNMENT ...... 28
2.11 1024 OR 4096 CYLINDER LIMIT .................................................... 28
2.12 64K BOOT CODE LIMIT................................................................. 30
CHAPTER 3. INSTALLING AND UNINSTALLING ACRONIS OS SELECTOR... 31
3.1 GETTING STARTED ........................................................................31
3.2 INSTALLATION............................................................................... 32
3.3 REPAIRING/UPGRADING ACRONIS OS SELECTOR......................... 34
Copyright © SWsoft, 2000-2002 5
CHAPTER 4. BOOT MENU .............................................................................. 35
4.1 BOOTING OPERATING SYSTEMS..................................................... 36
4.2 RUNNING ACRONIS OS SELECTOR TOOLS .................................... 37
4.3 TUNING ACRONIS OS SELECTOR .................................................. 37
CHAPTER 5. ACRONIS OS SELECTOR SETUP ............................................... 39
5.1 AUTOMATIC SETUP OPERATION MODE......................................... 39
5.2 ACRONIS OS SELECTOR SETUP MAIN WINDOW ........................... 40
5.3 TWO VIEW MODES OF CONFIGURATION LIST ............................... 42
5.4 MANIPULATING AN OPERATING SYSTEM CONFIGURATION.......... 44
5.4.1 SETTING A DEFAULT CONFIGURATION .....................................................44
5.4.2 COPYING................................................................................................... 44
5.4.3 DELETING .................................................................................................44
5.4.4 HIDING ..................................................................................................... 45
5.4.5 EDITING CONFIGURATION PROPERTIES..................................................... 45
5.5 MANIPULATING AN OPERATING SYSTEM...................................... 47
5.5.1 COPYING................................................................................................... 47
5.5.2 DELETING .................................................................................................47
5.5.3 HIDING ..................................................................................................... 48
5.5.4 EDITING OPERATING SYSTEM PROPERTIES ...............................................48
5.5.5 DELETING THE INFORMATION ABOUT REMOVED HARD DISK ................... 50
5.6 SPECIAL CONFIGURATION LIST ITEMS .......................................... 51
5.6.1 BOOT FROM FLOPPY SECTION ..................................................................51
5.6.2 SEPARATOR ..............................................................................................52
5.6.3 COMMENT ................................................................................................ 53
5.7 ACRONIS OS SELECTOR OPTIONS ................................................. 54
5.7.1 STANDARD OPTIONS.................................................................................55
5.7.2 INPUT DEVICE OPTIONS ............................................................................ 55
5.7.3 PASSWORDS..............................................................................................56
5.8 OS DETECTION WIZARD ............................................................... 57
5.8.1 INTRO PAGE..............................................................................................57
5.8.2 PARTITION PAGE.......................................................................................57
5.8.3 BOOT SECTOR SELECTION PAGE............................................................... 58
5.8.4 SEARCH RESULT PAGE ............................................................................. 59
5.9 DEACTIVATING ACRONIS OS SELECTOR ...................................... 60
5.10 UNINSTALLING ACRONIS OS SELECTOR....................................... 60
CHAPTER 6. DISK ADMINISTRATOR ............................................................. 62
6.1 RUNNING DISK ADMINISTRATOR .................................................. 62
6.2 DISK ADMINISTRATOR MAIN WINDOW SURVEY .......................... 62
6.3 DISK ADMINISTRATOR INTERFACE ............................................... 64
6.3.1 USING THE MOUSE ...................................................................................64
6.3.2 USING THE KEYBOARD .............................................................................65
6.4 DISK ADMINISTRATOR APPEARANCE SETUP MENU ........................
(«V
IEW» MENU) ............................................................................ 65
6.5 PENDING OPERATIONS .................................................................. 66
6.6 GETTING HELP............................................................................... 67
CHAPTER 7. MAIN OPERATIONS WITH DISK ADMINISTRATOR.................. 68
7.1 CREATING A PARTITION ................................................................ 68
7.1.1 CREATING BOOTABLE PARTITIONS........................................................... 69
7.1.2 CREATING A PARTITION WITH DISK ADMINISTRATOR ..............................70
7.2 COPYING OR MOVING A PARTITION .............................................. 72
7.3 RESIZING A PARTITION.................................................................. 74
7.4 FORMATTING A PARTITION ........................................................... 75
6 Table of Contents
7.5 DELETING A PARTITION ................................................................ 75
7.6 CHANGING THE PARTITION LABEL................................................ 76
7.7 VIEW DETAILS ABOUT A PARTITION ............................................. 77
7.7.1 GENERAL PROPERTIES SHEET...................................................................77
7.7.2 FILE SYSTEM PROPERTIES SHEET ............................................................. 78
7.7.3 ERRORS SHEET .........................................................................................78
7.8 GETTING DETAILED INFORMATION ABOUT A HARD DISK ............ 79
7.8.1 STANDARD PROPERTY SHEET ...................................................................79
7.8.2 HARD DISK PROPERTY SHEET .................................................................. 80
7.8.3 EXTENDED PROPERTIES SHEET ................................................................. 81
7.8.4 EDD PROPERTIES SHEET..........................................................................81
CHAPTER 8. ADVANCED OPERATIONS WITH DISK ADMINISTRATOR ........ 82
8.1 CONVERTING A PARTITION ........................................................... 82
8.2 CHANGING THE PARTITION TYPE.................................................. 83
8.3 SETTING AN ACTIVE PARTITION ................................................... 84
8.4 HIDING A PARTITION ..................................................................... 84
8.5 RESIZING CLUSTERS/BLOCKS ....................................................... 85
8.6 RESIZING THE FAT16 ROOT FOLDER............................................ 86
8.7 MOVING A PARTITION IN THE PARTITION TABLE ......................... 87
CHAPTER 9. PARTICULARITIES OF OPERATING SYSTEM FUNCTIONING ... 89
9.1 DOS-TYPE OPERATING SYSTEMS.................................................. 89
9.1.1 SUPPORTED VERSIONS..............................................................................89
9.1.2 BOOT SEQUENCE ......................................................................................89
9.1.3 SYSTEM AND CONFIGURATION FILES........................................................ 90
9.1.4 LIMITATIONS ............................................................................................ 91
9.2 WINDOWS 95/98/ME..................................................................... 91
9.2.1 SUPPORTED VERSIONS..............................................................................91
9.2.2 BOOTING DETAILS AND LIMITATIONS ...................................................... 91
9.2.3 SYSTEM FOLDERS ..................................................................................... 92
9.2.4 DETAILS ON WINDOWS 95/98/ME INSTALLATION .......................................
WITH ACRONIS OS SELECTOR .................................................................. 92
9.3 WINDOWS NT/2000/XP ................................................................ 93
9.3.1 SUPPORTED VERSIONS..............................................................................93
9.3.2 BOOTING PECULIARITIES .......................................................................... 93
9.3.3 SYSTEM AND CONFIGURATION FILES........................................................ 94
9.3.4 SYSTEM FOLDERS ..................................................................................... 94
9.3.5 LIMITATIONS ............................................................................................ 95
9.4 LINUX ............................................................................................ 95
9.5 OTHER OPERATING SYSTEMS........................................................ 95
CHAPTER 10. WINDOWS 95/98/ME INSTALLATION WIZARD ..................... 97
10.1 WIZARD START ............................................................................. 97
10.2 PREPARATION TO UPGRADING WINDOWS 95/98/ME .......................
WITHOUT SAVING ITS OLD VERSION............................................. 98
10.3 PREPARATION TO UPGRADING WINDOWS 95/98/ME .......................
WITH SAVING ITS OLD VERSION ................................................... 99
10.4 PREPARATION TO NEW WINDOWS 95/98/ME ..................................
O
PERATING SYSTEM INSTALLATION........................................... 100
CHAPTER 11. INSTALLING/UPDATING WINDOWS NT/2000/XP................ 102
11.1 INSTALLING A NEW WINDOWS NT/2000/XP .............................102
11.1.1 STARTING THE INSTALLATION ................................................................102
11.1.2 1
ST
INSTALLATION STAGE ....................................................................... 104
Copyright © SWsoft, 2000-2002 7
11.1.3 2
ND
INSTALLATION STAGE ....................................................................... 105
11.2 INSTALLING WINDOWS 2000/XP .....................................................
V
IA UPGRADING WINDOWS 95/98/ME ....................................... 105
11.3 INSTALLING WINDOWS 2000/XP .....................................................
BY UPGRADING ANOTHER WINDOWS NT/2000/XP.................... 108
11.4 RESTORING (REPAIRING) AN ALREADY-INSTALLED ........................
W
11.4.1 GAINING ACCESS TO WINDOWS NT/2000/XP BOOT MENU ................... 109
11.4.2 RUNNING WINDOWS NT/2000/XP SETUP PROGRAM ...................................
TO RESTORE AN ALREADY INSTALLED OPERATING SYSTEM ..................109
INDOWS NT/2000/XP OPERATING SYSTEM ............................ 109
APPENDIX A. TEXT EDITOR ........................................................................ 111
A.1 GENERAL INFORMATION ............................................................. 111
A.2 MAIN FUNCTIONS ........................................................................ 111
APPENDIX B. DISK EDITOR ......................................................................... 113
B.1 RUNNING DISK EDITOR ...............................................................113
B.2 NAVIGATING DISK EDITOR ......................................................... 114
B.3 VIEW MODES............................................................................... 114
B.3.1 HEXADECIMAL MODE............................................................................. 115
B.3.2 PARTITION TABLE MODE........................................................................115
B.3.3 FAT16/FAT32/NTFS BOOT SECTOR MODE ...............................................
OR FAT32 FS INFO SECTOR MODE ........................................................116
B.4 SIMPLE EDITING AND UNDOING CHANGES ................................. 116
B.5 EDITING IN THE PARTITION TABLE MODE .................................. 117
B.6 USING BLOCKS AND CLIPBOARD ................................................ 119
B.7 SEARCH ....................................................................................... 120
APPENDIX C. ACRONIS OS SELECTOR ON-LINE HELP ............................ 121
C.1 CONTROLS ................................................................................... 121
C.2 USING THE MOUSE ...................................................................... 121
C.3 USING THE KEYBOARD ................................................................ 122
APPENDIX D. COMPATIBILITY WITH OTHER SOFTWARE ......................... 123
D.1 DOS FDISK ................................................................................123
D.2 NORTON UTILITIES ...................................................................... 123
D.3 DISK COMPRESSION SOFTWARE.................................................. 124
D.4 OTHER BOOT MANAGERS ........................................................... 124
D.5 ANTI-VIRUS SOFTWARE............................................................... 124
D.6 DISK OVERLAY SOFTWARE ......................................................... 124
APPENDIX E. FAQ (FREQUENTLY ASKED QUESTIONS) ........................... 126
APPENDIX F. GLOSSARY ............................................................................. 129
8 Table of Contents
About This Guide
The purpose of this Guide is to help in using Acronis OS Selector and solving
problems that might arise while working with it.
User Guide consists of the following chapters and appendices:
Chapter 1 «Introduction» provides an overview of Acronis OS Selector and its
main features.
Chapter 2 «Basic Information» makes the user acquainted with the basic
concepts, terms and principles that are necessary when working with Acronis
OS Selector.
Chapter 3 «Installing and Uninstalling Acronis OS Selector» tells how to
install and uninstall Acronis OS Selector and what other actions the
Installation program performs.
Chapter 4 «Boot Menu» describes the appearance and functioning of Acronis
OS Selector Boot Menu.
Chapter 5 «Acronis OS Selector Setup» gives detailed description of Acronis
OS Selector Setup and all the configuring options that are provided by its
interface.
Chapter 6 «Disk Administrator» provides a description of Disk Administrator’s
interface and basic working principles.
Chapter 7 «Main Operations with Disk Administrator» provides detailed
information and instructions for performing the most common operations
with partitions in the Disk Administrator, such as creating, formatting,
moving and resizing.
Chapter 8 «Advanced Operations with Disk Administrator» explains how and
what for one can use advanced features of Disk Administrator, such as
resizing clusters, changing partition type, etc.
Chapter 9 «Particularities of Operating System Functioning» describes the
particularities of functioning of different operating systems in the context of
their operation together with Acronis OS Selector.
Chapter 10 «Windows 95/98/ME Installation Wizard» gives detailed
information about how the Installation Wizard can be used to install or
upgrade Windows 95/98/ME operating systems.
Appendix A. «Text Editor» contains the description of the text editor that is
provided with Acronis OS Selector.
Copyright © SWsoft, 2000-2002 9
Appendix B. «Disk Editor» acquaints the user with the additional feature –
direct sector-by-sector hard disk editing.
Appendix C. «Acronis OS Selector On-Line Help» covers the functioning of
the Acronis OS Selector built-in hypertext On-Line Help.
Appendix D. «Compatibility with Other Software» describes how different
programs react on partition structure and actions performed by Disk
Administrator.
Appendix E. «FAQ (Frequently Asked Questions)» answers some frequently
asked questions about Acronis OS Selector.
Appendix F. «Glossary» contains the main terms that are used in this
Guide, and the Acronis OS Selector interface, together with brief
explanations.
10 About this Guide
Chapter 1. Introduction
This chapter contains the following general information about Acronis OS
Selector:
Acronis OS Selector as a Boot Manager
Acronis OS Selector as a Partition Manager
Acronis OS Selector Key Features
Main Disk Administrator features
Acronis OS Selector System Requirements
How does Acronis OS Selector Function?
What is a Boot Context?
1.1 Acronis OS Selector as a Boot Manager
The main function of a boot manager is to allow the user to install multiple
operating systems on one computer and to choose the necessary one when
the computer is booted.
All boot managers can be divided into several complexity levels:
1. Boot managers that are able to boot an operating system by reading the
boot sector from the first sector of a partition. These boot managers do
not recognize file systems and hence cannot support multiple operating
systems that are installed on one partition. They have the simplest user
interface and occupy minimum disk space. The examples are OS/2
BootManager and Linux’s LILO.
2. Boot managers that can load the boot sector from a file with a specified
name. These usually are parts of an operating system (built-in boot
managers) that are supposed to somehow help the operating system to
co-exist with other operating systems. Built-in boot managers have the
simplest user interface. Examples are: NT OS Loader.
3. Full-scale boot managers that can detect file systems (FAT), recognize
different operating systems, and are able to automatically detect them.
These boot managers are aware of system and configuration files of
operating systems and are able to create backup copies of them, to allow
the user to have multiple operating systems with same system file names
or multiple copies of configurations of one operating system on one
partition. Examples are: BootWizard 3.x, System Commander, BootIt.
4. Only Acronis OS Selector 8.0 can be put on the last, highest level of
complexity. Unlike all other boot managers, it allows users to have
multiple operating systems with same named system folders on one
Copyright © SWsoft, 2000-2002 11
partition and allows hiding any specified partitions from any given
operating system.
Aside from performing its main function, Acronis OS Selector has many
additional features.
1.2 Acronis OS Selector as a Partition Manager
When new operating systems are installed, hard disks are replaced or added
and in some other cases the necessity arises in relocating the information on
hard disks. That is why the Acronis OS Selector distribution package now
includes Disk Administrator – a program that allows users to easily perform a
variety of operations with partitions such as creating and deleting, formatting
and resizing on the fly without data loss, moving and copying.
Because of the limitations in the FAT16 file system that is used in many
popular operating systems such as MS-DOS and Windows 95/98/ME, up to
40% of disk space might be wasted. With help from our Disk Administrator
you will be able to easily analyze the waste and reduce it by choosing
appropriate partition or cluster sizes or converting the partitions to the FAT32
file system. Reverse conversion is also possible.
With the same ease the Disk Administrator can perform various actions with
NTFS, Linux Ext2/Ext3, Linux Swap, and even Linux Ext3 and ReiserFS
partitions.
You can also get detailed information about the hard disk drive geometry and
partitions, as well as view and edit their content sector-by-sector.
1.3 Acronis OS Selector Key Features
Here the key features of Acronis OS Selector as a boot manager are listed:
• Supports more than 100 operating systems on one computer.
• Supports operating systems both on primary and logical partitions of any
hard disk.
• Can boot both from A: and B: floppy drives.
• Supports multiple operating systems on one FAT partition.
• Automated backing up and restoring the critical system and configuration
files, such as IO.SYS, MSDOS.SYS, COMMAND.COM, CONFIG.SYS etc.
• Detects possible boot virus infection.
• Ability to establish password protection on Boot Menu and any operating
system configuration.
12 Chapter 1 : Introduction
The following features are unique to Acronis OS Selector:
• Standardized intuitive user interface.
• Power-off from Boot Menu.
• Flexible Boot Menu appearance adjustment.
• Fast creating and adjustment of different configurations of an operating
system.
• Actions that can be performed from the installation media (usually a
bootable diskette or a CD-ROM), such as activating and deactivating
Acronis OS Selector, uninstalling it, running Disk Administrator etc.
• Supports operating systems with same system folder names (like
Program Files) on one partition.
• Very flexible adjustment of boot context for each operating system
including the possibility to hide any partition. A special mode is provided
to hide partitions for Windows NT, 2000, and XP operating systems.
• Can be installed on any FAT16 or FAT32 partition of any hard disk or on
a separate partition that will be hidden from all operating systems.
• Increased stability in case of partition structure and hard disk
configuration changes.
1.4 Main Disk Administrator features
Disk Administrator has the following main features:
• Create and format FAT16, FAT32, NTFS, Linux Ext2/Ext3, Linux ReiserFS
and Linux Swap partitions;
• Convert FAT16<=>FAT32 partitions without data loss;
• Copy and move any partitions;
• Resize FAT16, FAT32, NTFS, Linux Ext2/Ext3, Linux ReiserFS and Linux
Swap partitions on the fly without data loss;
• Select cluster/block size and any other file system parameters manually;
• Delete partitions of any type;
• Edit partition label;
• Adjust logical partition chain parameters automatically;
• View partition and file system parameters;
• Optional usage of 64-kilobyte clusters.
Copyright © SWsoft, 2000-2002 13
g
g
The following features are unique to Disk Administrator:
• Choose the precise position of a partition on the disk and in the partition
structure (primary/logical), its size, file system type, label, and cluster
size (when the partition is created, moved or resized). All these actions
can be performed in one pass.
• As a result, you can copy a partition to free space of smaller size.
• Built-in sector-by-sector hard disk and partition editor.
• Different sorting modes of the partition list.
• View partition letters and numbers and their changes for different
operating systems.
• Support of hard disks of any type (IDE, SCSI) and of any size that are
visible through BIOS in any mode (Normal, Large, LBA), including the
extended BIOS functions.
• View detailed hard disk information.
1.5 Acronis OS Selector System Requirements
Acronis OS Selector requires the following hardware:
• CPU – at least i386.
• RAM – at least 16MB (we recommend having more memory when
working with large hard disks and partitions).
• Disk space – 2MB plus extra space on any FAT16 or FAT32 partition to
store backups of system files of detected operating systems. If there are
no FAT partitions on the computer, the installation program helps to
create a special partition to install Acronis OS Selector.
• 3.5-inch floppy drive – to install from an installation diskette.
• CD-ROM – to install from CD-ROM.
• Video-card and monitor – VGA-compatible (VBE 2.0 compatible video-card
is recommended).
• Mouse – handy, but not mandatory.
Acronis OS Selector may conflict with boot virus checkers that are built into many
existing BIOSes because Acronis OS Selector frequently modifies the contents of
MBR and boot sectors. This function should be disabled for proper Acronis OS
Selector installation and functioning. Some anti-virus software may also alert you for
possible virus presence for example in the REINSTAL.COM file. If you have
to suspect that the computer is really infected, perform the necessary dia
and cures and then restore Acronis OS Selector from clean installation media.
rounds
nostics
14 Chapter 1 : Introduction
1.6 How does Acronis OS Selector Function?
During the installation on your computer, Acronis OS Selector writes its own
code into the MBR of the first hard disk, and thus gains control before any
other operation system. The old MBR content is stored in the \BOOTWIZ\
MBRBACKS.DAT file to enable a restore of the configuration as it was before
Acronis OS Selector installation. Acronis OS Selector MBR contains the
information about what hard disk and partition holds the main part of the
boot manager. With help from this information, the MBR code loads the
Acronis OS Selector boot sector (it is located in the
\BOOTWIZ\BOOTSECT.SYS file) and passes control to it. In turn, this boot
sector code looks for the BOOTWIZ.SYS (Acronis OS Selector Loader) file in
the root folder and loads it. The loader checks if any changes were done to
the partition structure and boot sectors since the last execution. If there are
any changes then \BOOTWIZ\ BOOTCFG.EXE (Acronis OS Selector Setup) is
automatically executed. It then tracks the changes and tries to find any new
operating systems with their help. The configurations of the newly found
operating systems are automatically added to the Boot Menu configurations.
The \BOOTWIZ\ BOOTMENU.EXE program is then executed. This is the
Acronis OS Selector Boot Menu itself.
The Boot Menu allows you to choose which operating system to boot. The
boot manager itself performs all the actions that are necessary for the
preparation of boot context for the selected operating system and passes
control to its boot sector. Then the operating system is booted normally
without any help from Acronis OS Selector.
1.7 What is a Boot Context?
Every operating system configuration that was detected by Acronis OS
Selector has its own boot context that includes the following elements:
• Operating system partition (operating system boot partition, partition of
system files). Such partitions are marked with a «Boot» flag in Acronis OS
Selector Setup interface.
• Boot sector of an operating system (for operating systems installed on
FAT partitions). Operating system is booted by loading it to memory
address 0000h:7C00h and executing it.
• Boot sector modifiers. Some modification of the boot sector data is
needed to allow certain operating systems to be booted from a logical
partition and/or from non-first hard disk. Acronis OS Selector allows
modification of the following parameters: BIOS extension usage for
MS-DOS 7.1/8.0 (Windows 95OSR2/98/ME), hard disk number, absolute
boot sector number, or boot partition letter for OS/2.
Copyright © SWsoft, 2000-2002 15
• System files of an operating system that are backed up by Acronis OS
Selector in its own folder and are copied by it to their place (usually the
root folder of the operating system partition) before booting the
operating system. Backing up the system files allows the installation of
multiple operating systems with same system file names, like IO.SYS,
MSDOS.SYS, COMMAND.COM, NTLDR etc. on one partition.
• System folders of an operating system that are copied by Acronis OS
Selector from its folder where they are stored to their proper place
before the operating system is booted. It allows multiple operating
systems with same system folder names to share one partition while
preventing possible conflicts. System folder names usually include
Windows or WinNT, Program Files, etc. A partition where folders with
these names are stored is called a system folder partition of an operating
system. Such a partition is marked with a «Win» flag in Acronis OS
Selector Setup interface.
• Hidden partition list for an operating system. Hiding any specified
partitions from an operating system allows very flexible changes in letter
assignment to partitions by the operating system and some more exotic
things like booting operating systems, that cannot execute without
Acronis OS Selector, from different hard disks and logical partitions.
• Active partition list for an operating system. For some operating systems
the order of letter assignment depends on which primary partitions are
active. For each operating system, Acronis OS Selector allows separate
selection of active partitions on all hard disks.
• LBA partition support flag that defines if there is any need to set LBA type
for partitions that can only be accessed via BIOS extension.
• Configuration files of an operating system configuration. These are files
that Acronis OS Selector backups in its folder and copies back to their
place (usually the root folder of the operating system partition) before
the operating system is booted. Backing up configuration files allows
users to have multiple configurations of an operating system on one
partition that differ only by the contents of their configuration files (the
latter being usually CONFIG.SYS, AUTOEXEC.BAT, BOOT.INI etc.).
16 Chapter 1 : Introduction
Chapter 2. Basic Information
This chapter elaborates on basic concepts that are related to hard disk
partitioning. This will help you to better understand and use Acronis OS
Selector.
2.1 What is a Hard Disk?
A hard disk is a part of a computer that is used for long-term information
storage. Unlike Random Access Memory (RAM) that loses all the data when
the power is switched off, a hard disk continually stores data, thus allowing
the saving of programs, documents and other information. Hard disks also
have much higher capacity than RAM; modern hard disk capacity can exceed
hundreds of gigabytes.
2.1.1 Hard Disk Architecture
A hard disk consists of the following basic parts: magnetic platters, axis,
read/write heads and integrated electronics.
• Magnetic platters actually are the hard disks that are made of metal or
plastic that gives the name to the entire device. Both sides of each
platter are covered with iron oxide or some other magnetic material.
• Magnetic platters are installed on one spindle and rotate on it as one
body.
• For each side of each platter there is a separate read/write head. The
heads are also joined together and move radially with respect to the
magnetic platters, thus allowing access to any point of any platter.
• Integrated electronics are used to process computer commands, magnetic
platter rotation control, read/write head movements and for data
buffering and transfer of it between the hard disk and the computer.
2.1.2 How does Hard Disk Work?
In a computer, all data is stored as bit sequences. On hard disks each bit is
stored as a magnetic charge (positive or negative) on the magnetized platter
surface. When a computer saves the data, it sends it to the hard disk as a
sequence of bits, the hard disk receives the data, positions the magnetic
heads and records the information received with their help by magnetizing
the platter surface. Reading the data from a hard disk is done in a similar
way.
Read/write heads can access any point of any platter at any time, so the
data may be stored and read with high speed in a random sequence (unlike
sequential access to data on magnetic tapes).
Copyright © SWsoft, 2000-2002 17
2.2 Hard Disk Formatting
A computer needs to have access to the necessary information at any time,
but even the smallest of hard disks can hold millions and millions of bits. So
how does a computer know where to look for the data required or where to
store the new data? Dividing the disks into small easily identifiable parts
solves this problem. This allows the computer to easily find the needed data.
The process of creation of such parts is called formatting. There are two
levels of formatting:
• physical formatting (or low-level formatting),
• logical formatting.
2.2.1 Physical Formatting
Physical formatting of a hard disk must be performed first. Usually users do
not have to worry about this, since the manufacturer usually provides lowlevel formatting. Physical formatting divides the surface of the magnetic
platters into tracks and sectors.
• Tracks are concentric circles that are drawn on magnetic surfaces by the
magnetic heads. The tracks are assigned numbers from zero and up
center wards.
• Tracks in their turn are divided into small areas that are called sectors
and contain a fixed amount of data. Usual sector size is 512 bytes (1
byte is equal to 8 bits).
• All tracks that can be accessed without moving the read/write heads
form a cylinder. Track number and cylinder number are all the same.
Access to data inside one cylinder is much faster than re-positioning of
heads from one cylinder to another.
Over time the magnetic surface gradually loses its properties and there
appear areas where data storage becomes impossible. Sectors that fall into
these areas are called bad. Fortunately the quality of modern hard disks is
such that they usually become outdated before failing. Most modern hard
disks are also able to substitute bad sectors with good ones from a special
reserve. But if bad sectors appear, they should be software treated, for
example by marking them so that they are not used.
2.2.2 Logical Formatting
A physically formatted disk also must be logically formatted. Logical
formatting means that a file system is created on the disk so that files can be
written to it or read from it. Different operating systems (OS) use different
file systems, so the way the disk should be formatted depends on the OS you
want to install.
18 Chapter 2 : Basic Information
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g
For more detailed information about file systems see paragraph 2.3 «File Systems».
Formatting of a whole hard disk for one file system heavily limits the number of
operatin
can be solved. Prior to logical formatting a hard disk it must be
partition can then be formatted with its own file system. This will allow installin
different OSes. Partitioning also allows more efficient use of disk space.
For more detailed information about partitions see paragraph 2.4 «Partitions».
systems that can be installed on this hard disk. Fortunately this problem
2.3 File Systems
All file systems consist of structures that are necessary for data storage and
management. These structures usually include the operating system boot
record, folders and files. File systems perform the following basic actions:
1. Allocated and free space (and bad sector) tracking.
partitioned. Each
2. File names and folders support.
3. Tracking of physical file positions on the disk.
Different file systems are used by different operating systems. Some
operating systems can use only one file system, while others are able to use
multiple ones. Let us now go into more details about some of the most
widely used file systems.
2.3.1 FAT16
FAT16 file system is used widely in DOS-compatible operating systems (DRDOS, MS-DOS, PC-DOS etc.), Windows 95/98/ME, Windows NT/2000/XP, and
is supported by most of the other operating systems.
Main FAT16 features are the file allocation table (FAT) and clusters. FAT is
the core of the file system. For better security several copies of FAT exist
(usually 2). A cluster is the minimum data storage unit in the FAT16 file
system. One cluster contains a fixed number of sectors that equals to a
power of 2. FAT stores the information about which clusters are free,
allocated or bad, and also tells which files are stored in which clusters.
Maximum FAT16 file system size is 4 GB, maximum number of clusters is
65525 and maximum cluster size is 128 sectors. Usually the minimum cluster
size that results in not more than 65525 clusters is chosen. The more the
partition size the more the cluster size has to be. Many operating systems
work with 128-sector clusters incorrectly, thus reducing the maximum size of
a FAT16 partition to 2 GB.
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Usually the larger the cluster size the greater disk space losses (waste) become. For
more detailed information about cluster size management see paragraph 2.6
«Managing Partitions».
The FAT16 file system, like many others, has a root folder. But unlike all
others its root folder is stored in a special place and is limited in size
(standard formatting creates a root folder with 512 entries). Acronis OS
Selector Disk Administrator allows you to change the size of the root folder
for an existing partition.
Initially FAT16 had file name limitations of 8 characters in name and 3
characters in extension, but long file name support in Windows 95 and
Windows NT eliminated this limitation. OS/2 also supports long names, but in
another way. Yet another is used in UMSDOS file system that allows the
Linux operating system to work on FAT disks.
2.3.2 FAT32
FAT32 operating system first appeared in Windows 95 OSR2 and is also
supported in Windows 98/ME and Windows 2000/XP. FAT32 is an extension
of FAT16. FAT32 mainly differs from FAT16 by 28-bit cluster numbers and
more flexible root folder that is no longer limited in size. The reason for
creating FAT32 was the need to support large (more than 8 gigabytes) hard
disks and the impossibility of building more complicated file system into
MS-DOS that remains the base for Windows 95/98/ME.
Maximum FAT32 file system size is 2 terabytes.
2.3.3 NTFS
NTFS is the basic Windows NT/2000/XP file system. Its organization is kept
secret, so no other operating system fully supports it. Basic NTFS structure is
an MFT (Master File Table). NTFS stores a backup copy of the MFT’s critical
part to decrease the probability of data damage and loss. All other NTFS data
structures are special files (metafiles).
NTFS, like FAT, uses clusters to store files, but cluster size is independent
from partition size. NTFS is a 64-bit file system; it uses Unicode to store file
names, with a journaling (or so-called failure-proof) file system, that
supports compression and encryption.
Files in folders are indexed to speed up search routines.
2.3.4 Linux Ext2
Ext2 is the basic file system for the Linux operating system. Ext2 is a 32-bit
file system, its maximum size is 16 terabytes. The basic data structure, which
describes a file, is an I-node. Area to store the table of all I-nodes should be
allocated in advance (during formatting). Acronis OS Selector Disk
20 Chapter 2 : Basic Information
Administrator allows you to change the size of i-nodes table for an existing
partition.
2.3.5 Linux Ext3
Officially introduced with their version 7.2 of the Linux operating system,
Ext3 is the Red Hat Linux journaling file system. It is forward and backward
compatible with Linux Ext2. It has multiple journaling modes and broad
cross-platform compatibility in both 32- and 64-bit architectures.
2.3.6 Linux ReiserFS
The ReiserFS file system was officially added to Linux in 2001. ReiserFS is
free of most of Ext2 disadvantages; and it is a 64-bit journaling file system
with dynamic allocation of memory for data structures.
2.4 Partitions
As previously mentioned, a physically formatted disk has to be partitioned.
Each partition may be viewed as an independent unit that can be formatted
with any desirable file system.
2.4.1 When is it Useful to Have Multiple Partitions?
Formatting the whole hard disk with one file system is not always the best
way to use your disk space and resources. On the contrary, several partitions
allow you to:
• Install more than one operating system;
• Use disk space more effectively and efficiently;
• Physically separate programs and data according to functions or some
other feature.
2.4.2 Partition Structure on a Hard Disk
A special place – a partition table – is left in the very first sector of the hard
disk (this sector is called MBR, or Master Boot Record) to store information
about the hard disk partitioning. This table consists of four entries and
contains the following information about the partition:
• Status (a flag that shows if a partition is active);
• Type (0 – the entry is empty);
• First sector number;
• Size in sectors.
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Status flag of a partition on the first hard disk usually tells the default MBR
code that boot should be performed from this partition. Partition type
identifies it with a certain operating system. An operating system usually
recognizes only partitions with the numbers it knows and ignores the rest.
Such table structure has the following limitations:
• Maximum amount of partitions is four;
• Maximum number of types – 255;
• Maximum supported hard disk size is 4 terabytes.
The first limitation proved to be the most serious, so partition type 5 is now
used not for partition description but as a reference to the sector where another
partition table is located (let us call such partition table the extended partition
table). Thus it became possible to have an unlimited number of partitions on a
hard disk.
Partitions whose information is stored in MBR are called primary, while all
others are known logical partition. The point of such division is that many
operating systems can only be booted from a primary partition and only on
the first hard disk.
Most operating systems impose the following limitations on partition
structure of a hard disk:
• There can be only one primary partition for this operating system and it
is booted from it. All other primary partitions should be of types that are
not recognized by this OS;
• In the MBR partition table there can be only one reference to a partition
table and such extended partitions must include all the logical partitions
of this hard disk;
• Primary partitions should not overlap with the logical partition;
• Each extended partition table may hold only one usual partition and only
one reference to a partition table;
• Each partition table must be located in the first sector of a cylinder;
• Each subsequent table must be located further from the beginning of the
hard disk then the previous one;
• A partition that is described in an extended partition table must be
located right after it, usually at the beginning of the next track.
The limitation of only one reference to a usual partition and only one
reference to a partition table results in all logical partitions of a hard disk
forming a linear chain.
22 Chapter 2 : Basic Information
2.5 Boot Sequence
2.5.1 Very Beginning
Whenever a computer is turned on or rebooted, control is given to BIOS
(Base Input/Output System) that is stored in the computer ROM. BIOS
initializes and tests the hardware and then loads the first sector from the
boot disk device (usually it is the first hard disk, and the sector is the MBR)
and passes control to it. All the actions that follow depend on the contents of
this sector.
Some words should be said about how the hard disks are counted. BIOS
assigns hard disks sequential numbers starting from 080h, the sequence is
defined by the order in which the disks are plugged into IDE controllers
(Primary Master, Primary Slave, Secondary Master, Secondary Slave), next
follow the SCSI hard disks. This sequence would be broken if you change the
boot sequence in the BIOS setup. Thus if you have set that booting should
be done from hard disk E (do not confuse letters that are assigned to the
hard disks by BIOS with partition letters!), then the sequence would start
with the disk that would have otherwise been the third (usually its Secondary
Master). In Acronis OS Selector BIOS hard disk sequence is used, but the
initial number is 1.
2.5.2 Booting without the Boot Manager
Usually the MBR of the hard disk contains the code that is written there by a
standard partitioning program (FDISK) and performs the following actions:
• Searches the partition table for the first partition that is marked as
active;
• Attempts to load into memory the first sector of the partition found. Such
sector of a partition is called the boot sector;
• Passes control to the loaded sector.
The boot sector usually contains the code that attempts to boot an operating
system from the partition. Each operating system has its own boot code.
2.5.3 What does the Boot Manager do?
Installing a boot manager on your computer slightly changes the boot
sequence. Usually the boot manager writes its own code into the MBR that
loads into memory, not the boot sector of an operating system, but the boot
manager’s code. A boot manager usually offers you a choice of operating
systems to boot, and the booting of the chosen operating system happens
only after your selection.
Copyright © SWsoft, 2000-2002 23
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2.6 Managing Partitions
2.6.1 Setting an Active Partition
If you do not have a boot manager but you have created several primary
partitions, then you must select a partition from which the operating system
will be booted. There is a status flag for that in the partition table. This flag
should be on only for one partition, and it should be a partition and not an
unused entry or a reference to the partition table.
Some modern BIOSes check the partition table to see if there is any active
partition in it before passing control to MBR.
Make sure that the partition is formatted and contains an operatin
setting it as active.
2.6.2 Accessing the Same Files from Multiple Operating Systems
There are several basic differences between primary and logical partitions (it
refers mainly to the FAT partitions):
• Most operating systems can boot only from a primary partition (excluding
OS/2, Linux, and with some limitations and with help of Acronis OS
Selector, Windows 95 OSR2, 98, and ME).
• Some operating systems recognize only one primary partition and ignore
all others (OS/2).
• All boot managers, except the Acronis OS Selector, must be installed only
on the primary partition of the first hard disk.
Considering these limitations one can decide which partitions to use for what
purposes. Primary partitions are best used to boot operating systems and
store system folders and files only. On the other hand, logical partitions can
be used to store all data, because they will be accessible by the operating
systems. If you are planning to install many different operating systems on
your computer, then those that can be booted from logical partitions are
better installed there to save primary partition space.
system before
2.6.3 Efficiency of Disk Space Usage
If you have a large hard disk, but must use the FAT file system, then you
should know some of its peculiarities to use the disk space more efficiently.
As previously discussed, the main FAT feature is breaking the partition into
clusters of fixed size ranging from 512 bytes to 64 kilobytes.
In FAT16, 16-bits are reserved to store numbers of clusters, so the maximum
number of clusters is 65525. The result is that the bigger the partition size
the bigger the cluster is needed, and the maximum partition size is about 4
gigabytes. However bigger cluster size results in higher hard disk space
24 Chapter 2 : Basic Information
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losses (waste) due to the adjustment of allocated space to cluster
boundaries.
The following table gives the approximate dependence of these losses (hard
disk waste) versus the cluster size:
Partition size Cluster size Wastes
<127M 2K 2%
128÷255M
256÷511M
512÷1023M
1024÷2047M
2048÷4096M
4K 4%
8K 10%
16K 25%
32K 40%
64K 50%
One of the ways to reduce losses is to break the disk space into smaller
partitions. The other is to use the FAT32 file system where 32 bits are
assigned to the cluster number (28 bits actually), raising the maximum
partition size to 4 terabytes. But FAT32 has its own drawback:
• If clusters size is small and partition size is big then the file allocation
table size increases, and may lead to slowing down the booting of the
operating system and file access.
2.7 Hidden Partitions
Disk Administrator allows you to hide partitions. Hiding is done to prevent an
operating system from detecting a partition, assigning a letter to it and
accessing its files, i.e. the partition becomes invisible to the operating system
and the applications that run under it.
Hiding partitions is useful when important data should be protected from
unauthorized or occasional access. Unlike other software Acronis OS Selector
can hide any partition regardless of their type, or whether they exist as
primary or not. A special mode is provided to hide partitions for Windows NT,
2000, and XP operating systems.
Be careful when creating several primary partitions, and leaving all of them visible
since some operatin
experience trouble in handling them.
systems (Windows 95/98/ME being first on the list) may
Copyright © SWsoft, 2000-2002 25
2.8 Drive Letters
Most operating systems when booting assign letters (C, D,...) to all partitions
on all hard disks. You, your applications and the operating system itself
identify file placement in a partition using these letters.
An operating system may change letter assignment if you plug or unplug
hard disks or perform different actions with partitions. Some changes in
letter assignment may lead to troubles in parts or in the entire configuration
of an operating system. This usually happens when letters are changed for
the partitions where the system files and folders of an operating system are
stored.
To avoid such changes in configuration and/or to solve the problems
associated with drive letters, you should know the following:
• How the operating systems assign letters to disks.
• What problems arise if the letter order is changed?
• What actions should be performed during partition management to avoid
changing the letter order?
• How to solve the problems that arise with unavoidable changes.
2.9 Assignment of Letters in Different Operating Systems
2.9.1 MS-DOS 5.0-6.22, MS-DOS 7.0, Windows 95 (original)
These operating systems assign letters in a fixed order. This order has
settled with the evolution of MS-DOS and abides by the following rules:
• Letter assignment begins with letter C: and goes on to letter Z:. Letters
A: and B: are reserved for floppy disk drives.
• A partition to which the letter C: was assigned is treated as the boot
partition, i.e. the partition from which the operating system was booted.
So if the partition from which the operating system will boot is assigned
a letter that is different from C:, most probably the booting will not
execute properly.
• Only partitions of types 1 (FAT12), 4, 6 (FAT16) are recognized. The real
type of file system is determined by the contents of the partition and not
by its type. Partitions of all other types are skipped.
• Only the first suitable partition is looked for in any extended partition
table, the rest are ignored.
• Records of type 5 (Extended) are treated as a reference to the next
partition table, and only the first reference in any partition table is
followed, all other records are ignored. Thus all the logical partitions
form a linear chain.
26 Chapter 2 : Basic Information
• The first suitable active primary partition from the first hard disk is
looked for. If there is none then the first suitable primary partition is
looked for.
• Then the first suitable primary partitions of the rest hard disks are looked
for in a similar way.
• Then all the suitable logical partitions are looked for following the chain
on the first, then on the second, the third etc. hard disk.
• Then all the remaining primary partitions of the first, second etc. hard
disks are looked for.
Letter sequence in Windows 95 may differ slightly from that of the MS-DOS
7.0, if drives are connected to the computer that are partially visible or
completely invisible to BIOS. Letters to partitions on such devices will be
assigned after all the letters from MS-DOS 7.0.
2.9.2 MS-DOS 7.1/8.0, Windows 95 OSR2/98/ME
The order of letter assignment in these operating systems is similar to
previous ones with the following exceptions:
• Additional partition types are recognized: 11 (FAT32), 12 (FAT32 LBA)
and 13 (FAT16 LBA), resulting from FAT32 and large hard disk support.
• Additional partition type 15 (EXTENDED LBA) is recognized as a
reference to the next partition table.
FAT16 LBA, FAT32 LBA and Extended LBA partition types mean the same as FAT16,
FAT32 and Extended respectively, but additionally inform MS-DOS 7.1/8.0 that these
partitions should be accessed through BIOS extension.
2.9.3 OS/2
Letter assignment for this operating system is similar to that for MS-DOS 5.0
with the following exceptions:
• Partition status is ignored, i.e. on the first step the first suitable primary
partition is looked for.
• Partitions with type 7 (HPFS) are also looked for.
• All the primary partitions except the first ones are completely ignored.
2.9.4 Windows NT/2000/XP
These systems differ from all the rest that use letters for disks, because it is
possible to change the letter that is assigned to a partition. Initial assignment
though is similar to that for MS-DOS 5.0–7.0 (for Windows NT 3.x) and for
MS-DOS 7.1/8.0 (for Windows NT 4.0, Windows 2000/XP). Windows NT 4.0
does not support the FAT32 file system but does assign letters to FAT32
partitions. One should also keep in mind that letter assignment for these
systems may differ heavily from that for other operating systems since it
Copyright © SWsoft, 2000-2002 27
does not matter if hard disks and other disk drives that are connected to the
computer are visible to BIOS or not.
When changing the structure of partitions it is necessary to make sure that
the letters for the partitions where the swap file (\PAGEFILE.SYS) do not
change, otherwise the system may become unbootable.
2.10 Troubles Arising from Changing Letter Assignment
Changing letters may damage your application setup. For example, let us
suppose that you have installed several applications on a certain partition
that at that moment had letter D: assigned to it. You have decided to create
shortcuts to these applications so that it would be easy to run them under
Windows 95. Every time you run an application via a shortcut, Windows
addresses to the partition D: in order to find and run corresponding software.
If the letter for this partition is changed, the shortcut will point to an
incorrect partition, and Windows will be unable to find the software to run
the application since now the letter D: is assigned to another partition.
Changing partition letters usually affects all system configurations that are
based on original partition letters. Those are usually the settings from
AUTOEXEC.BAT, CONFIG.SYS, WIN.INI, SYSTEM.INI, and several other
configuration files, and also in Windows 95/98/ME and Windows NT/2000/XP
system registry.
Letter assignment usually changes when the following changes to the
partition structure are performed:
• A partition is created.
• A partition is moved.
• A partition is deleted.
• An extra hard disk is plugged in.
• Some hard disk is unplugged.
Some letter changes may be avoided by using our partition hiding function.
Acronis OS Selector allows the hiding of any partition from any operating
system.
2.11 1024 or 4096 Cylinder Limit
For a long time the main way to access hard disks was through BIOS, i.e.
interrupt 13h functions. In order to read or write to a disk three bytes had to
be passed containing cylinder number (10 bits), head number (6 bits) and
sector number (6 bits), so that the hard disk size was limited to 2016
megabytes. To overcome this limitation there was an attempt to use the
leftover 2 bits, thus raising the maximum capacity to 8064 megabytes. But
28 Chapter 2 : Basic Information
since this was done in different ways, there appeared several BIOS
functioning modes:
• Normal. In this mode cylinder number takes 12 bits, and head number
takes 6 bits, allowing for 4096 cylinders and 64 heads.
• Large and LBA. In these modes cylinder number takes 10 bits and head
number takes 8 bits, allowing for 1024 cylinders and 256 heads.
Few operating systems support the Normal mode. In the LBA mode errors in
operating systems in calculating the hard disk parameters result in limitation
of 255 heads, limiting the size to ~8032 megabytes.
BIOS extension that allowed addressing sectors via absolute numbers instead
of cylinder, head, and sector numbers was a considerable advance. Absolute
number takes 64 bits, thus allowing addressing hard disks of enormous
capacity.
So the troubles with limitations arise in the following cases:
• If an application (or an operating system) does not support BIOS
extension, it will be able to see not more than 1024 * number_of_heads
* sectors_per_track sectors or 4096 * number_of_heads *
sectors_per_track sectors if the application supports the Normal mode,
usually these are 8064 megabytes.
• If the program has an error in calculating hard disk parameters (all
MS-DOS version have this error), and BIOS reports 256 heads on the
hard disk.
• If BIOS does not support extension (usually these are BIOSes that were
released before 1994).
In some BIOSes even the extension does not allow to address more than
8064 megabytes.
BIOS problems can be solved by installing some program like EZ-Drive, DM6
DDO, MaxBlast, that uploads its own interrupt 13h code that is free of abovementioned disadvantages. Acronis OS Selector whenever possible works
through BIOS extension and is fully compatible with EZ-Drive type programs.
Copyright © SWsoft, 2000-2002 29
2.12 64K Boot Code Limit
Some operating systems, namely MS-DOS 6.x and earlier versions, and
Windows NT 4.0 and earlier versions, have an error in the boot code in
converting the absolute sector number into cylinder, head, and sector
numbers. They suppose that the result of division of absolute sector number
by the number of sectors per track will not exceed 16 bits, i.e. 64 K. Since
most modern hard disks have 63 sectors per track, this results in 2016megabyte limitation of boot code location.
Be careful when moving a partition containing an operating system with the abovementioned limitation since the operating system may become unbootable.
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