I concur with Matt and Pete, the list of programs looks clean, although you have a lot running.
I’d start buy getting rid of one of the virus scanners, just keep one and make sure its updated regularly. Also make sure Windows is fully up to date - make sure you’re using Microsoft Update and not Windows Update, there's a link on the Windows Update site.
Are you using Windows Media Centre? If not you could disable all its services.
Also make sure when you run a full system virus scan, that its set to scan all files, including inside compressed files.