It's pretty simple actually... you just download the .iso of windows XP with your favorite mac torrent client, mount it to a DVD, start an application called BOOTCAMP to partition your hard drive and use the DVD as the windows install disc. Once windows is installed on it, you basically have mac and windows on the same computer. just hit "option" to choose between them when the computer starts up. It was a little more difficult for me cause i used the windows 7 release client and had to crack it after i installed it, but yea windows xp should work.
or just buy a pc.
