The bios is independent of Windows and is in memory on the motherboard, not on the hard drive.
If you have a full installation Windows XP CD you should be able to format the drive (use NTFS not Fat 32) and do a fresh install of Windows XP.
Make sure you have the 25 digit Windows key handy for the computer on which you are reinstalling XP.
(this key must have never have been used on any other computer but this one or it won't activate)
How to perform a Clean Install Windows XPhttp://www.michaelstevenstech.com/cleanxpinstall.html
Edited by Enthusiast, 15 November 2006 - 10:14 PM.