Just wanted to add that I like Avast a lot... I used to only use Norton, but that became true bloatware (for a while) and although they've improved it a lot, I had moved away... went to TrendMicro for a little bit, then the 3 A's... Avg, Avira and Avast... At the end of the day, Avast was the one for me. I still use 4.8 on my wife's computer for now, (little netbook) where an even smaller footprint is a good thing.
Whenever Avast settles down to its 6.1 release, I'll buy the pro version. V6 is really quite impressive when compared to 4.8, so somebody is doing something right and System Explorer doesn't hate the memory footprint, so...