Agree with epiccs.
1.I'm use Ontrack Disk Manager 7.x running from diskette in advanced maintenance mode to fix this problem first.
2.Then, if all working O'k, You can install WIN95/98 and it should kill made by DM changes in boot sector.
3.If not - use Norton Disk Doctor (often called as Norton Disk Destroeyer,if You want) from NU8 (on FAT16 partitions) running with option:
ndd c:/rebuild.
I have save lots of HDD from trash doing so.
Of course, all information on this HDD will be lost.
4.Another possible source for this problem - bad MoBo' cashe. Try to disable MoBo cashe and reboot.