ClamWin is a simple, powerful and most importantly, free antivirus checker for Microsoft Windows.

The program features an easy to use GUI and the developers claim high detection rates for viruses and spyware although it doesn't seem to find anything extra or beyond what other anti-virus scanners find. The full program is facilitated by regular virus database updates so that's its generally always updated with the latest threats to your system. Unfortunately ClamWin Portable has scheduled scans and updates disabled so that the program is not locked in huge updates every time you activate it on the move. The downside of this of course is that it's never up to date with the latest threats. The big advantage of this version of course is that you can take it pretty much anywhere on a USB stick. However, the program does not feature a real-time scanner which means that scanning for protection is down to you. You have to manually scan your system with the program every so often to see if you have been infected with anything.

Free, portable and easy to use, this is a decent anti virus solution let down by the fact that it doesn't scan in real time nor update itself automatically unless prompted.