I installed windows xp on one computer. i took that hard drive out that has windows xp on it and stuck it in another computer. it booted just fine in the first computer but not the other computer.
If you installed XP and it's not coming up, you either didn't do the reformat correctly, have the boot squence wrong, or the installation got corrupted somehow. Try it again.
And...um...hopefully you aren't trying to install XP on the machine you have listed in your sig. (twitches)
i dont know how it worked, but i installed win xp on that comp. when it had only a 2 gig HDD. It still is running. It is very slow but it is the only computer so far that hasn't given me any problems.