Most people seem to think that they are completely protected using just one anti-virus program, but this is certainly not the case. If you use programs like Limewire or Bittorrent you will collect a lot of viruses, and will run into trouble in a short matter of time without the appropriate software to protect you pc.
Most anti-virus programs only find a small percentage of the malicious software out there and some virus scanners barely find any viruses at all including most of the common store bought, well known virus scanners that are very trusted.
Although there are plenty of good scanners on the web, there seem to be a few free scanners that stand out from the rest and when used in conjunction will find basically every virus. Malwarebytes Anti-Malware, SUPERAntiSpyware, Spybot Search & Destroy, Avast and Spyware Doctor.
Malwarebytes, SUPERAntiSpyware and Spybot can all be downloaded
