With services tweaked, a bunch I just don't need running, anti-virus totally shut down, and nothing running, "gaming mode" I call this, 16 active process' on XP. Same situation on Vista, 32. Literally twice as many.
Doesn't really bother me tho, except, when actually gaming. I did actually notice my big games, like a very heavy resource using huge game like Company of Heroes, running MUCH better on XP. I've been dual booting for a while just to play with Vista every once in a while, but its definitely still XP Pro as my main.