Install an anti-virus program

An anti-virus program is required to secure your computer against viruses, spyware, worms, and trojans. AVG is the currently recommended version due to the additional email protection it gives you. Recommended Settings: Options > Advanced Settings > Email Protection > Email Scanner > Certification -- Disable certify incoming and outgoing. It is annoying for you and others. Note: Avast! is a highly recommended alternative if you so choose, http://www.avast.com/en-us/index. I didn't put it here because one of the rootkit scanners uses the Avast database during its one time scans and if you do that regularly, this setup should give you maximum coverage.