I have been a card carrying member of the "If it's free, it's for me" club for a couple years, and did fine with AVG, spybot, ad-aware, scotty Winpatrol, Hijack This!, etc...
Well, this morning I clicked on a not so nice link(as I am oft to do), and within 2 minutes my machine was acting like it just swallowed a vile of small pox. I did my usual AVG, Spybot, Ad-Aware regimen and things started getting really kooky. It would boot up, but wouldn't complete. The icons would flash on and off, as if false-starting. Couldn't get high jack this to start, and finally it just sat there in windows, but no icons would show. Safe Boot didn't work, boot from the D drive didn't work, nothing.
I was forced to go and actually purchase something. For years, Norton was known as a resource hog. As of late though, I've heard they improved that and it got the best rating this year. So, I went with Norton 360, their complete suite.
All things are a go.