I'm sorry but I'll have to disagree with kev. I think Vista is a piece of ... and chews up resources like mad. Chances are if you're getting a new computer you won't notice it (they're designed to run with Vista after all...) but if you downgrade to XP, it will literally fly. Here's what the survey says:
http://www.downloadsquad.com/2008/08...ngraded-to-xp/
Downgrading takes a bit of work however. Here's a nice article on the topic:
http://www.computerworld.com/action/...icleId=9040318
First you'll have to have Vista business or ultimate (if they offer home, you could spend a few extra bucks to get business or ultimate, which will grant you xp downgrade rights bundled). Then you have to hunt for drivers. It's a bit of work, but it's doable and the results are very satisfying for those who sucessfully did it.