From what I can recall with that OS, it may stop working altogether if it detects an entirely different motherboard + CPU combination. So, even installing drivers for an entirely different board won't help anything. You would simply have to either wipe the drive clean and re-install XP anew (with support having been recently ended, I'm not certain whether it can still be activated post-install), or move all the components out of your work computer's case and into the HP case with the good power supply.
"Never interrupt your enemy when he is making a mistake.
"Why can't EVERYTHING be rocket propelled?!"
-Mattias Nilsson, Mercenaries 2: World In Flames