How can I backup/restore my Master Boot Record?

A. A. The Windows NT Resource kit supplies a utility DISKSAVE.EXE which enables a binary image of the Master Boot Record (MBR) or Boot Sector to be saved.

DISKSAVE has to be run from DOS and so you will need to create a bootable DOS disk and copy DISKSAVE.EXE to the disk. To create a DOS bootable disk just use the command

C:> format a: /s

from a DOS machine (do not do it from a Windows NT command session).

Once you boot with the disk you will have a number of options:

F2 - Backup the Master Boot Record - This function will prompt for a path and filename to save the MBR image to. The path and filename are limited to 64 characters. The resulting file will be a binary image of the sector and will be 512 bytes in size. The MBR is always located at Cylinder 0, Side 0, Sector 1 of the boot disk.

F3 - Restore Master Boot Record - This function will prompt for a path and filename for the previously save Master Boot Record file. The only error checking is for the file size (must be 512 bytes). Copying and incorrect file to the MBR will permanently destroy the partition table information. In addition, the machine will not boot without a valid MBR. The Path/filename is limited to 64 characters.

F4 - Backup the Boot Sector - This function will prompt for a path and filename to save the Boot Sector image to. The path and filename are limited to 64 characters. The resulting file will be a binary image of the sector and will be 512 bytes in size. The function opens the partition table, searches for an active partition, then jumps to the starting location of that partition. The sector at that location is then saved under the filename the user entered. There are no checks to determine if the sector is a valid boot sector.

F5 - Restore Boot Sector - This function will prompt for a path and filename for the previously save Boot Sector file. The only error checking is for the file size (must be 512 bytes). Copying and incorrect file to the Boot Sector will permanently destroy Boot Sector information. In addition, the machine will not boot without a valid Boot Sector. The Path/filename is limited to 64 characters.

F6 - Disable FT on the Boot Drive - This function may be useful when Windows NT will not boot from a mirrored system drive. The function looks for the bootable (marked active) partition. It then checks to see if the SystemType byte has the high bit set. Windows NT sets the high bit of the SystemType byte if the partition is a member of a Fault Tolerant set. Disabling this bit has the same effect as breaking the mirror. There is no provision for re-enabling the bit once it has be disabled.