ClamWin is a good open source antivirus program for Windows (the Unix version is called Clam AV, the engine behind Clam Win).
From my tests it has a nice detection rate. It has automatic downloads, shell integration (where you can use its functions through right-click). It also has plug ins for email verification.
The bad thing about ClamWin is that it doesn’t have (yet) a real-time scanner so you’re left at manually run system checks.
Read More →