I'm currently running 18 processes (Firefox and TaskManager incl.)
How many are you running? (Hit CTRL+ALT+DEL to see process manager. Current processes are at the bottom left corner of the dialog).
Anything over 30 or so is usually too much, unless you have a lot of windows open for a specific task.
BTW: A lot of processes can lead to laggy scrolling, especially in the case of onboard video cards.