All the Details of many versions of

both MBR (Master Boot Records)

and OS Boot Sectors ( also called:

Volume Boot Records)







These pages will probably remain in a state of flux (change) as we continue to gather new data for Boot Records, filling in Assembly code comments and adding important topics related to booting up your box (computer) !

You may also wish to explore our newly revised Feedback page containing suggestions for booting-up your PC when the disk drive has failed to do so: Feedback page.

Personalized Data Recovery help via E-Mail (for a reasonable fee). But you can always write to us here with any questions for help you may need or your comments.

Index to MBR (Master Boot Record) and VBR (Volume Boot Record) or OS Boot Sectors

( with COLOR Highlighted Views of how these appear on your drives ):

As either a review or an introduction (for those who need definitions and explanations of the terms used), we suggest that everyone read or at least glance over: Disk Drive Terminology. These terminology pages include useful details (even experienced techs should read them!) such as:  How do you calculate the exact capacity of a floppy disk or hard drive?  ,  Why do some utilities show less drive capacity than what's printed on the HDD?  ,  What do MiB and GiB mean?  and  Do you know that partitioning a drive on a computer with a BIOS made earlier than 1999 will most likely waste some drive space on an archaic structure known as a Test or Diagnostic Cylinder? 

How many Sectors are on a Hard Drive? -- Contains useful tables for picturing the contents of your hard drive.



Some Miscellaneous Topics:

An Introduction to Data Recovery .

How To Permanently Erase ALL the DATA On A Hard Disk -- without physically destroying your drive !

How to change your BOOT.INI Menus under Win2000/XP

HDD and OS Disk Limits: 32GB, 64GB, 137GB etc.!!!

6 to 64-bit Hex Numbers ( and Basic Partition Table Limits )



Partition Magic writes "28 96 C4 17" to an HDD's 1st Track

55AAh is the Wrong Way to describe the Boot Signature on a PC

Explains why many have misunderstood how to refer to the byte sequence 55h followed by AAh on a PC: It's due to the little-endian architecture of PCs and incorrect usage in the documentation.



Free Software:

References. Links. Free Tools, Utilities and Boot Managers:

MBR, Partition Table and Boot Record Tools and Links .











MBRs (Master Boot Records)





The Windows™ 7 and 8 GPT (GUID Partition Table) 'Protective' MBR and EFI Partition -- The MBR created by a running Windows™ 7 or 8 OS (Disk Management) when choosing to 'Initialize' (partition) a drive as GPT. The Partition Type identifier will always be: "EE" hex.

The Windows™ 7 / 8 / 8.1 MBR -- The MBR created by a running Windows™ 7, 8 or 8.1 OS (Disk Management) or its install DVD when installed to a completely blank hard drive or a disk with existing Windows OSs; includes details about the partition layout and sizes of Windows 7 and 8 OS installs.

The Windows™ Vista MBR -- The MBR created by a running Windows™ Vista OS (Disk Management) or its install DVD when installed on either a completely blank hard drive or a disk with existing Windows OSs; includes some details about the Vista OS.

The Windows™ XP/2000 MBR -- The MBR created by a running Windows 2000 or XP OS (specifically Disk Management) when used to install a completely blank hard drive on your system; includes details about the Win 2k/XP Disk Signature bytes!

The Windows MBR for FAT32 -- The MBR created by FDISK from Windows 95B (or OSR2), Windows 98/98SE and even Windows ME.



The Standard MBR --- This is the Master Boot Record that's placed on the first sector of any hard disk partitioned by FDISK.EXE ( or FDISK.COM ) from all versions of MS-DOS back to MS-DOS 3.30 (including DOS 6.22 and MS-Windows 95 "A" also known as MS-DOS 7.0).

This is also the same as the Standard IPL (or MBR) code used by many early Boot Managers and TestDisk (before version 5.7 when it was changed) and some boot managers when there's a problem that requires the MBR code to be written again.



Why Use This Code? -- Examination of an odd MBR that people sometimes put in their MBR sector when trying to recover data.



Notes on DOS 3.30 and an early (1988) OEM version -- The Master Boot Record created by the NEC® (Revision 3) version of MS-DOS 3.30's FDISK was slightly different than that of all the other MS-DOS 3.30 MBRs ( in order to allow it to have 8 Partition entries in its Partition Table ) . Some important points about DOS MBRs in general are also included here.

The IBM® Personal Computer DOS 2.00 MBR and How Similar it is to the Standard MBR (of DOS 3.30) --- The Master Boot Record created by IBM ® 's DOS 2.00; showing each byte of code that's different from the Standard MBR.



The Ranish MBR/Compact Boot Manager -- Single sector MBR replacement included with the Ranish Partition Manager. Preliminary Listing only.

All about FDISK.EXE -- Covers all versions of Microsoft® FDISK.

Linux (and many other OSs) have "fdisk" programs that are safer for your data than Microsoft's FDISK; read the next selection about how MS-FDISK can destroy some of your data!

[ NOTE: Under Windows 2000/XP, FDISK has been replaced by a variety of methods for partitioning (setting up the MBR on) your drives:

1) The install CD when setting up a new system,

2) The Disk Management "MMC Snap-In" program,

3) The Recovery Console's command: diskpart (found on install CDs),

4) The diskpart command under the Command Prompt of Windows XP; even more difficult to use than the Recovery Console version of diskpart ! So, Disk Management is the best choice for most users! ] You could, of course, still use an old Win98 Boot Diskette's FDISK program to create a FAT32 partition.

What does FDISK.EXE do to a hard drive? --- Everyone still using DOS / Win 98 should read the last section entitled: "So What happens When FDISK overwrites Sectors on a Drive already containing Valuable Data?" before ever using the MS-FDISK utility!

OS Boot Records

NOTE: Ever since Windows 2000 (and then, of course, the Windows XP, 7, 8 or any later OS), Boot Records (both MBR and VBR, and associated boot files) have been created by:

1) The install process,

2) The OSs' Disk Management "MMC Snap-In" program (which partitions and formats), or

3) The CMD Prompt commands for partitioning (using DISKPART ) and formatting (using format ) a drive.



Of the last two, the Disk Management window is the easiest way for most users to accomplish the task of partitioning and/or simply formatting a new drive they attach to an existing system.



All about SYS.COM - Shows details of all versions of Microsoft® SYS.COM which can be used to create both Hard Disk and Floppy Disk OS Boot Records under DOS and earlier Windows versions.



1) HDD / SSD OS Boot Records



The Windows 8 / 8.1 (NTFS) Boot Sector (VBR) - The Win 8 (NT5.x?) Boot Sector (or VBR); there are some changes compared to the Win 7 VBR, but it's still mostly the same. Exceptions: One of the error messages has been removed, it uses slightly different message offsets and code and there is a different value used in its testing for existence of TPM 1.2. It continues to use a BOOTMGR file, but there are a number of changes in its "Bootstrap" code! Overall, it's structure is still similar to earlier NTFS Boot Records.

The Windows 7 (NTFS) Boot Record Sector - The Win 7 (NT5.x?) Boot Record sector; except for the new code bytes (11 of them), it's rather similar to the Windows Vista VBR. It slightly refines testing for TPM 1.2, and continues to use the Vista BOOTMGR; again, it's structure is similar to the earlier NTFS Boot Records.

A Comparison of Windows™ Vista, 7 and 8 VBR Code - This page first shows the VBR code as color highlighted hex bytes for each of these OS Boot Sectors side by side, showning their differences, and then line by line as Assembly instructions.

The Vista (NTFS) Boot Record Sector - The Windows Vista (NT5.x?) Boot Record sector; except for the new code (which also tests for TPM 1.2) and its tests for BOOTMGR, it's quite similar in structure to earlier NTFS Boot Records.

The NTFS Boot Record: Boot Sector - The Windows 2000 (NT5.0) and XP (NT5.1) Boot Record; including the NTFS BPB (BIOS Parameter Block). Link to "The Disk Editor View page" to view the Record as it would be seen in a disk editor.

The NTFS Boot Record: Bootstrap (NTLDR Loader) Code - The Windows 2000 (NT5.0) and XP (NT5.1) "Bootstrap" Sectors. . . which we refer to as the NTLDR Section of the NTFS Boot Record Area.

The FAT32 Boot Record under Windows 2000 or XP - The VBR created by Windows 2000/XP/2003 for a FAT32 partition, or what your old Windows 9x/Me VBRs (see MSWIN4.1 VBR) in the first partition of the first drive will be changed into when installing Win 2000/XP on that system.





MSWIN4.1 Boot Record - For the Windows 95B, 98 and 98SE and ME OS (or FAT32 ) Boot Records; including the BPB ( BIOS Parameter Block ) .











2) Back to Basics: Floppy Disk Boot Records



MSWIN4.1 (Windows 98) Floppy Disk Boot Record -- For Booting the underlying MS-DOS 7.1 of the Windows 98 O perating S ystems from a Floppy Diskette . Preliminary Listing.

MS-DOS 5.0 Floppy Disk Boot Record -- For Booting the MS-DOS 5.0 to 6.22 Operating Systems from a floppy diskette.



The IBM® Personal Computer DOS 1.10 Boot Record

IBM's Personal Computer DOS 1.10. These pages include facts about IBM's first International DOS version.

The IBM® Personal Computer DOS 1.00 Boot Record

IBM's Personal Computer DOS 1.00. These pages include many other fascinating facts about the original PC's software.





Boot Managers (MBRs)



Windows Vista, 7, 8 / 8.1 and later use what is called BOOTMGR (instead of the NTLDR; under Windows XP/2000) and you can examine and make some changes to its BCD (Boot Configuration Data) "Store" using its command line BCD Editor; or, some of the free GUI BCD Editors that others have created:

The Windows 2000/XP/2003 BOOT.INI Menu system

This is related to various system files, such as NTLDR, which may even appear in a Windows 98/ME partition if you install Win XP/2000/2003 onto the same computer!

GRUB - The GRand Unified Boot Manager! -- This one is now the default Boot Manager for some distros such as Red Hat. You may even consider using this Boot Manager for Microsoft OSs (after installing a small Linux /boot partition for the GRUB executable and support files); this is how The Starman used to run his own multi-boot systems. (He's since then decided to use more Virtual machines instead.)



LILO (Linux Loader) Boot Manager's MBR -- This used to be the only Boot Manager for the Linux OS, and it was the best choice for many Linux projects such as a Linux Boot Disk Rescue System.

Confused? Send us an e-mail if you have a specific question about the MBR or other Boot Records...

Updated: February 25, 2009; August 16, 2009; March 11, 2011; March 30, 2012; June 2012; January 2013; June 2015.

Last Update: January 30, 2018.