A cool and undocumented feature of MICROS~1 fdisk is the /mbr flag. This will rewrite the MBR of C:. It will not do anything to a second hard drive that has been formatted with format /s, believe me, I've tried. So you'll have to take out the primary hard drive and boot from floppy to do that.

Anyway, to use this feature, simply type fdisk /mbr to rewrite your boot record. I often instruct Linux newbies to do this when they want to get rid of LILO. But beware, one time this screwed up a partition table of mine.