press F8 and try to boot up in safe mode...
if that doesnt work try inserting your OS CD, but if you cant even get into BIOS that wont work either, Hmmm I got to think about this one a bit...
Did you try reseating the cable? remove/reseat/reboot? If then maybe: total cost $12 buy a new floppy drive, make sure they give you a cable, remove both the existing cable and floppy install new one and reboot again...
tell us how it goes