I have a P4 HT 3gHz. I usually have other stuff running also; like a DVD, Firefox, Yahoo Widgets, Majong Tiles, and I leave the logging of events and stuff going. If something crashes, I like to know why.
So, there is a lot of background tasks. Once in a while, usually to play new games, I boot into a less busy environment. But I like to have all my toys and gizmos.