AVG is a virus program that bundles adaware and spyware - - all in one. I've been running the FREE version for almost 2 years and never have a problem. Here's a link to the FREE version:
http://free.avg.com/us-en/download
BEFORE you download, uninstall your McAfee.
The other thing you might try to make your PC run faster is to do a de-frag.