uninstall compaq presario c500 laptop bios

hi, i hv installed xp sp2, i hv updated my bios, now it’s not detecting hdd, in bios it’s there. i installed ubuntu os there is no prob. but now i m not able to reinstall xp.. its telling hdd is not detected.. any one can help to solve this prob. i hv downloaded bios from hp site for my product only… help me pls..