Is my Bios corrupted? Please advise ....

Dear All, I'm using the Asus P4S533E motherboard and
have just installed a 1 GB DDR module which works
well with all of my programs.
My problem is, the 1.44 Mb 3.5inch floppy ( set correcty
in Bios ) is recognised as a 1055.2 Mb floppy in Win'98SE
and Win XP !!
The computer won't even boot in DOS to a system disc
in the floppy drive.
I've tried 3 different Floppy drives (and connecting cables)
with the same result.
For these reasons, I think maybe the Bios is corrupted.....
I need help in locating the latest Bios files to flash the BIOS
chip on the Net and would be grateful for any help as I am
new to this ....
Also, I am wondering how I can go about flashing the BIOS
from DOS prompt with no access to the Floppy drive? Can
Bios flashing be done from Windows?
Thanks for any help/ suggestions.