Here's my anti-virus plan since the above Alureon.A trojan scare...
1. Stop using Windows if possible. Move to an alternate OS, linux (example: ubuntu) or Mac OS or Chromium. This is not because the other OS is inherently any safer, it's just that virus coders target Windows because more people use it - so they get more bang for their "hard work".
2. If using Windows, install as few additional software as possible - for example: don't install Java if you do not need it. CCleaner is a good tool to audit all installed software and remove what you don't need.
3. Choose automatic updates for Windows and all installed software.
4. Use alternatives to common Microsoft programs targeted by virus coders. Examples: use Chrome instead of Internet Explorer, and replace Outlook with Thunderbird or simply use a web based email like gmail on the browser.
Per #1 above, I have moved my daughter's desktop to Ubuntu (she never had a problem with the switch - todays kids are naturals with technology), replaced my wife's laptop with a Samsung Chromebook (she loves it's simplicity, speed, and light weight). Only the desktop connected to the TV for streaming content over the web (we got rid of cable) has Windows on it because some websites we watch only works on Internet Explorer. We also use LastPass on all the computers to avoid having to type passwords and have separate complex long passwords for every site.
“Our life is frittered away by detail. Simplify, simplify.” ― Henry David Thoreau