While a huge debate is ongoing about what security precautions to consider when using the internet, this is the setup I use, and have used for the last couple of years without incident.
Firefox Web Browser:http://www.mozilla.com/en-US/firefox/
AVG Anti-virus: http://free.grisoft.com/
AVG Anti-Rootkit:http://free.grisoft.com/doc/download-free-anti-rootkit/
Comodo Firewall Pro: http://www.personalfirewall.comodo.com/
Comodo VerificationEngine{anti-phishing protection}: http://www.vengine.com/
NoAdware Spyware Scanner {paid}:http://noadware.net/
SuperAntiSpyware Scanner: http://www.superantispyware.com/
SpywareBlaster{acts like a spyware firewall}: http://www.javacoolsoftware.com/spywareblaster.html
CCleaner{system optimizer and privacy tool}:http://www.ccleaner.com/
Use only one program at a time for a particular application to avoid confliction, and apart from NoAdware, all the programs listed above are free of charge.
Best of luck.