My father is always calling me about another virus he magically got and that I need to remotely log in and fix it for him.
My typical setup to prevent bugs is:
*Firefox or Chrome with Do Not Track opt out enabled in settings
*Adblock Plus add-on
*Avast! Antivirus
*ZoneLabs ZoneAlarm Free Firewall(they have a toolbar that is not optional to not install but it is easily uninstalled from the programs menu) Comodo Free Firewall is another option but is a little noisy with pop-ups for the novice use.
*Spywareblaster (adds blocked sites to the hosts file
*Spybot Search And Destroy v1.6 (also adds blocked sites to the hosts file. Versions 2.x I consider bloatware.) Can also scan for malware.
*Malwarebytes Antimalware Free (scan for malware only)
If you want a paid option, Bitdefender Internet Security Antivirus/Firewall combo - after searching for coupons such as back to school discounts, you can get a pretty good deal. I ended up getting 2 years for the price of 1 and it can be installed on 3 clients. It replaced Avast, ZoneAlarm and required I uninstalled Spybot but I put it back on so that I could keep the hosts file up to date. I believe it required Spybot to be uninstalled because v2.x runs in the background and is a conflict... But v1.6 does not run in the background and therefore not a conflict.
That's it. That's all I run and I don't get any nasties on my Windows installations, and I visit some pretty shady corners of the interwebs.