Zone alarm free firewall
Avast! free antivirus
Spywareblaster (get newest freeware version)
Ad aware (old freeware version)
Spybot search and destroy
Firefox browser 99% of the time
Thunderbird Email client
If you keep these programs updated, it's an effective and totally free way to go.
I haven't had so much as a bot in months and I surf in places that hold great promise for problems.