Bootsector of the IBM PC
The bootsector of the IBM PC and compatibles is also the partition table of the disk. It is also called Master Boot Record (MBR)
The MBR is 512 bytes large and is the first sector of a disk.
|0||440 bytes||Executable code|
|440||4 bytes||Disk MBR signature|
|446||64 bytes||Partition table|
|510||2 bytes||Boot signature (55 AA)|
When the signature is valid, the computer's BOOTROM will boot from the disk. To disable it, you have to wipe the signature bytes. You have the read the whole sector (512 bytes) and change only the signature and read back the sector.
A code example:
help requested see mailinglist archive at http://syslinux.zytor.com/archives/2006-October/007495.html
More information about the IBM PC bootsector is at
- some links
Microsoft have documented the FAT boot-sector format in KB-140418 Version 3 Dated December 6, 2003.