Because, in order for you to initially set up bootcamp you need a SP2 disk as the drivers on the leopard cd do not work with service pack 3... once you have bootcamp set up, run apple software update from xp, it will say bootcamp 2.1 is available... this update will then allow you to update to sp3...
Okay so if I buy the disc from the link on the first reply, then get it set up on BC, ill be able to run things like Guild wars or World of Warcraft on my Macbook?
also please done use abbreviations that a Mac noob wouldn't understand =P