Running Windows on a MacBook Pro 17"

[Riskwise]

I just ordered my MacBook Pro 17" and it is supposed to come today in like 2 hours. I plan on immediately running both Mac OSX, and Windows XP on it for poker. I went to the Mac Bootcamp site and they said I need a Windows XP install disc with service pack 2 on it. My computer is pretty old and when i got XP, the disc has service pack 1 on it. Do i need to buy windows XP all over again, or can i use a friends disc with service pack 2 on it for my machine too? I have a purchased copy of windows XP but i am totally clueless as to how the cd keys or duplicate security works. Is there anyone with any knowledge on this here?

Thanks.