might work if you don't have too many peripherals. Check and see the combined output on the 3.3v and +5v lines. If it's probably around 150w you should probably be okay. For XP's the minimum combined wattage seems to be around 180w. If it were me, I'd give it a shot and see if it works. I don't think it can do any damage, up to you though. Install Motherboard monitor or something and monitor your voltage readings and see how it goes.