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.
The first four are free but Spyware Doctor usually requires you to pay for it, however there is an easy way to download it free and legally. If you download Spyware Doctor from the official website it requires you to pay full price for a non trial version, but you can get the free version in the Google pack.
Malwarebytes, SUPERAntiSpyware and Spybot can all be downloaded here at j-web.
Although you need more than one virus scanner, a computer can only run one firewall, so it is important to choose a good one.
Windows firewall is not as good as it is made out to be, so is is bet to use a third party firewall such as ZoneAlarm which you can download for free at the ZoneAlarm website.
