|As mentioned, if you really need XP for a program that will not install under Windows 7, even under compatibility mode, install it as a virtual machine - the link above will give you the details. If you just want to 'play' with XP then resurrect an old machine of the right generation that will have XP drivers available for it, wipe the hard drive and do a completely clean installation. If you choose carefully (a decent dual core CPU), add a bit of additional memory and a generation old graphics card, and you can have a zippy little mess-around machine. You might just have one of these just laying around from before your last upgrade.|
You have to be a little bit crazy to keep you from going insane.