I used AVG (free) for years andit did a real good job. I have moved on to usingAntiVir(free ) as it is not so intrusive as AVG was and it has woorked out very well for the past year. http://majorgeeks.com/downloads29.html
You can find both on this page along with a choice of others as well.
**I'll admit when i saw this I expected it to be someone needing help uninstalling Norton or something similar
At one time I had 22 pages of single line script to remove Symantic from a system. I performed this registry editing ONE TIME ONLY. After that when someone asks about removing symantic I just tell them that because it is so embedded within the registry that the only way to remove it all is to reformat and reinstall.