HELP: Can boot UNIX from HD, CANNOT Boot DOS from Floppy

[Rao]

When I try to boot DOS (3.2) from my Floppy Drive (SCSI bus),
I get a Disk Boot Error, and the 5-1/4 in 1.2 M
Floppy spins uselessly.

However, I am able to boot ISC UNIX from the HD (SCSI,
Adaptec Controller). 

The  problem started when a friend CTRL-ALT-DeL when he was 
in the Diagnostic Mode, performing some Diag tests.

Please let me know how I can cure this.

Do I have to change the BIOS on the motherboard?

-bindu rama rao