I am looking for ways to secure my computer. What are the best free tools that I can use. - Bose

Based on past history, I highly recommend using the following free softwares:-
Anti-virus: AVG Anti-Virus Free Edition
Firewall: ZoneAlarm for novice users and Comodo Pro for advanced users.
Browser: Firefox
Anti-spyware: Ad-aware 2008 and Spybot S&D.