Install of xp

Hi, I just purchased a new imac and am making the switch from pc to mac. i would like to partition off a piece of hard drive and install xp with bootcamp to run games and other pc only apps.

My question is this: Is there anyway to use my liscense of xp from my old pc as my valid copy for boot camp? My copy was preinstalled; anyway to get a legit install onto the mac?

Thanks in advance,
~Thom