I tend to recommend against AVG, and suggest instead AntiVir or Avast.
http://antivirus.about.com/od/antivi...a/freeav_2.htm
Both are also free and have a higher detection rate than AVG.
As a general rule, I also suggest changing to a web browser like firefox, and install the adblock plugin. For additional security you can install the noscript plugin, though I found that one a bit of a hassle.
However, please realize that these programs stink at picking up adware. You'll need to install another program, like Spybot Search and Destroy, or Ad-Aware, both of which are also free. Of those, Ad-Aware is currently considered the "best".
The best for-pay system out there is Kaspersky, FYI. Highest detection rate, and also gets the spyware at the same time.
Please note, when I say best - that is based on the latest reviews. These are always somewhat subjective, and everyone always has an opinion one way or another. Be careful of anecdotal evidence from one user. You know how many computer illiterate people there are out there, and they are far more dangerous than any spyware
