I pretty much agree with pointblank, the big names seem to think the sole purpose of your PC is to scan for viruses, and they install massive packages.
I'd go with Stopzilla as Waffy says, and accept that not every AV application will clear every virus, so you might need to download another...eg AVG, or even a specific executable for a specific virus/malware.
Personally, I tend to run light, as I believe (possibly stupidly!!) I have a good idea about where virus/malware comes from, so I run AV all the time and malware app off, and scan manually
Also, don't run two AV or malware apps at the same time as your PC will probably expire.
just my 2c