What's vista doing in the background?

Ok so, of course i got Windows Vista. But any of you who are against vista, i will say im not using it as my primary OS. I also have Windows MCE on another partition. Although i will say Vista has improved alot since the beta and RC versions. I like it alot, its pretty and runs great on my machine. But what th ehell is it doing in the background? While im sitting there with nothing running and nothing but ad-aware and the ati control panel running, i here my hard drive working away and i notice on my sidebar the little cpu gadget going away hitting like 90% usage. It does go away after a minute or so. Now while its doig this Vista seems to run pefectly smooth but im wondering what process is running thats using up my precious rescources. Anyone else experiencing this? If so please share any information about it or how i can solve this, or if its even worth worrying about. My games seem to run fine. Just as good as XP, a times it gives a little lag over a period of 2 seconds every so often but other than that its fine. Maybe shutting down some uneaded processes will hep although it hought in Vista it was supposed to cut down the processes. ANd even shutown the aero glass theme while running games whcih it seems to do.