MalwareBytes.

AVG

Spybot Search and Destroy

Grisoft Zone Alarm (it gives lots of alerts until it “learns” your habits, but nothing would get through without you knowing.)

Trendwest Ad-Aware.

Avira
Spybot S&D

I have had good luck with Microsoft Security Essentials.

I have AVG and it works really well. It will probobly work on new ones best, too.

There’s a lot of offline protection, you should read some reviews and see which one best fits you.

For online protection, I suggest Norton Safeweb Lite.

I like Microsoft Security, too.

Also: [mod says] This is our Question of the Day!

Threatfire

Keep in mind that some good security practices are better than anti-virus programs.

-Create a separate user account for daily use.
-Do not use IE. Firefox and Chrome are better.
-Don’t click on e-mail attachments unless you expect them. My mom sent me the Paris Hilton sex tape and it was a exe file. But she didn’t actually send it. Something sent it to all her contacts. I did make a hundred bucks cleaning all that up for her.
-Do not install random shit from the internet. There are lots of scam sites with virus laden versions of legit software. I have searched for stuff on google and had the bad version rank higher than the real version.