You need an Intel Mac and a copy of XP Service Pack 2... and the bootcamp download - this 83mb download allows you to keep all your Mac data in place and still boot to XP.
Boot Camp burns a CD with all the Mac-specific drivers for Windows:All I can say is G'ON YERSEL' APPLE!!! There is now no excuse, other than cost, for not having a Mac.
* AirPort wireless
* The Eject key (on Apple keyboards)
* Brightness control for built-in displays
This CD also installs a Startup Disk control panel for Windows.