AntiVir
Download free antivirus protection - avira antivir personal official website.
http://www.free-av.com/
Avast
Avast! antivirus v4.8 represents a multi-award winning solution to virus protection, with anti-spyware and anti-rootkit technology built in for added security. it is available free for non-commercial, home use and with its fast, automatic updates, avast! antivirus is already being used by more than 50 million users worldwide to provide continuous protection against all forms of malicious software (malware).
http://www.avast.com/
AVG
Download antivirus and antispyware security software for windows for free, join the millions of home users that trust avg to protect their computers.
http://free.grisoft.com/freeweb.php/doc/2/
VCatch
VCatch
http://www.vcatch.com/download.html