I am completely opposed to using any program that requires itself to be continually running in the background for AV / security. I haven't run any in at least 5 years and have never once found anything even remotely suspicious on any Windows PC I run. I do one-off scans every few months as a precaution but I've yet to come across anything to be concerned about.

The number one priority has got to be to stop running IE. With a modern OS (eg: Win7) plus a modern browser such as Firefox, you really have to go out of your way to let any sort of spyware get onto a PC. A few generations back (XP / IE7 / FF2) I'd only recommend this approach for people who were very aware of what they were doing, but these days I think the situation is somewhat different.

The performance drain caused by any of these "active" scanners is still simply too great, even on a relatively high-performance machine, IMHO.