X has released a new visual style for XP based on Leopard, and it is perhaps the best Visual Style based on Leopard I have yet seen - and believe me, I've seen a lot! Check it our for yourselves at:

http://kspudw.deviantart.com/art/Leopard-X-76664828

With a few addons and extras, such as Styler, ObjectBar and ObjectDock, you will be able to get a very close OS X Leopard look on XP

Enjoy!