I'm definitely going with Avast or perhaps forget Antivirus all together.
After all, it's just the internet, how can I lose?
As far as forgoing an antivirus is concerned, it's mainly replaced by other solutions that work in tandem (along with heavily relying on common sense avoidance rules - amending user behavior itself to reduce threat). It's better to avoid the
root causes of infection first, than having to resort to after-the-fact removal - after-fact removal being what antivirus software is mostly used for, whether because of age not supporting real-time protection or because that's all you can get with the free versions.
If something
does get in, though, it's practically guaranteed that you have to know how to take care of it manually. The 'good' news is that doing it manually is generally very low on the resource-usage scale. It's just on the tedious side.
It also helps to know how to use Linux, since you could boot into that and essentially nuke the virus from orbit - seeing as how Linux can't be harmed by Windows viruses. That takes more care, though, because using Linux to clean up things in C:\WINDOWS\system32 (or other system-critical areas) can brick the Windows partition if things go bad.
Avast! actually does have a Linux version, though - I would assume mostly for the purpose of preventing it from acting as a carrier for Windows viruses, or to actually do cleaning of an infected Windows system from a safe location. In fact, that is the option I'd
really suggest - take the necessary precautionary measures on Windows, but have the antivirus software installed on the Linux partition since it's often the case that viruses embed themselves so deep into Windows' system that even going into Safe mode and running the antivirus there won't get them out. You'd have to be physically outside of Windows to get it clean, which an antivirus boot CD or running it from Linux would do.
