I assume you mean you want to retain your Windows XP install and are scared you cannot due to hardware changes?
Well, you'll be happy to hear there is a way around the Windows XP new hardware thing. Personally I got a new motherboard and new cpu, swapped over my old hdd, followed the steps, and no problem, no reinstall, it's still working nicely. There's no guarantee of course, so always back up first, but I know a few others it's worked for. Very simple, no dodgy programs or complex regediting required.
You'll probably struggle to find a k7s5a new now, but you can sometimes still find new SocketA boards going for not-too-much. Think someone was selling a SoA system on the sale forum here even...