nothing wrong with installing your exisitng XP on a new box
I've done it a number of times. You bought a license for that software. Put it on whatever box you feel like. You just can't put it on more than one unless you have a multi-license. When you register you may have to call Microsoft to tell them you are activating it on a new box. If so you will get a dialogue box that pops up with a phone number to call. They have never given me the 3rd degree about it, I just tell them I'm transferring the license to a new machine.
Steve G.