Bub & Anderson pretty much hit the nail on the head. You have to keep as many processes closed as possible. This can include everything from a chat program to an Adobe updater.
Please note: do NOT just go deleting things from your msconfig boot without knowing what they are first. If you aren't sure, search them at
http://www.processlibrary.org/Also, viruses can take up a TON of CPU usage. Download a virus scanner such as
avast! and run it to remove any viruses.
-Ian