AVG 7.5 ...a new and free version...I like it too. In combination with Zone Alarm...a must.

NOTE: They sometimes offer you the choice of "delete" or "quarantine". You should select quarantine if you are not 100% sure...then later clear this out if everything is still running if it should.

And from time to time, run CCleaner, Ad-Adware, Spybot - Search & Destroy.

There´s a range of pretty good free set-ups and some say it´s a better way to go since the big/popular names (like Norton) seem to get targetted by malware more often. In addition, many of these are lighter on resources, and some also run nicely in the background.
High marks being scored by newbies - worth checking out: SuperAntiSpyware, and a-squared.
If you wanna buy a system then get G-Data (which incorporates Kaspersky) or Trend Micro.

Run a few tests on your own system: www.auditmypc.com Maybe get a surprise!