Free Antivirus/Antimalware Software

It is recommended that you run only one antivirus program on your Windows machine at one time. The exception is Windows Defender, which is an antispyware application from Microsoft that is built into Windows Vista and Windows 7, and which runs alongside your antivirus application and detects spyware threats. All of these programs are free, and this list is by no means exhaustive. Please add comments relating to your experience with these programs as well as other recommendations.

Windows

• Microsoft Security Essentials: Free antivirus program from Microsoft, tightly integrated into Windows, and has excellent detection capabilities
• Windows Defender: Free antispyware application from Microsoft. Recommended if you use Windows XP or lower, already included in Windows Vista & Windows 7
• AVG Free: A robust, free antivirus package from Grisoft, one of the first popular free antimalware programs. AVG Free has come under fire lately for letting some malware fall through the cracks
• Avast! Home Edition: Free antivirus software that is lightweight and has good detection capabilities, although some have complained about the awkward user interface

Mac

• Sophos Anti-Virus for Mac Home Edition: Free antivirus software for Mac OS X.