Avast Antivirus

Avast! Antivirus is a free antivirus program developed by the Czech company ALWIL Software.  It has a virus database that gets updated on a regular basis, and has a user base of about 100 million users as of December 2009. avast! Antivirus contains anti-spyware technology along with rootkit protection, and has received many user awards in the past. The features found in this antivirus software are:

Like most free AV clients there is a paid version of this program as well that offers far better protection.

http://www.avast.com/en-us/index