Windows Tools & Utilities
AVG Antivirus, AntiSpyware, etc. by Grisoft
Win Patrol - Scotty Dog
Spybot - Search & Destroy
Mike Lins Startup Control Panel
Sysinternals - Source of many useful utilities
Ad-Aware 2007 Free
Sandboxie - runs your programs in an isolated space which prevents them from making permanent changes to other programs and data in your computer.