The NT Resource kit includes DISKSAVE.EXE which enables a binary image of the 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 "format a: /s" from a DOS or Win9x machine. Once you boot with the disk you will have a number of options:

F2 - Backup the Master Boot Record - prompts for a path and filename to save the MBR binary image.

F3 - Restore Master Boot Record

F4 - Backup the Boot Sector - prompts for a path and filename to save the Boot Sector.

F5 - Restore Boot Sector

F6 - Disable FT on the Boot Drive - 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.

For more background on the MBR: MBR Explained