|Whatever the problem is, one thing you can be 99.99% sure about, it is not the BIOS. BIOS do not just stop working. Besides, trying to update the BIOS on a computer that is not booting properly is the quickest route to total disaster.|
You problem is most likely to be hardware related. First try reseting the memory and then run a memory check. Check for overheating.
Trying to boot from a hard disk with Windows XP already on it from another computer never works unless the hardware on the computer it came from is identical the hardware you are trying to boot on.