You need to find a non-modified bios which is made for XP and flash your drive and then use the modified bios by myself and flash the drive as an upgrade...SONY is one of the hardest bios to flash after being modified...that is one sure way of it working.
The Lifebook Series of computers seems to give the most trouble for Toshiba...all others seem to work but that series.... The bios is correct in spite of it saying differently...I extracted the .ROM file from the the flash utility that came with it.... I am going to have to consult someone more experienced than myself about this problem...sorry, wish i had a better answer for you.