Microsoft Security Essentials
I have been using MS Security Essentials (MSSE) since the beta release for Windows Vista and Windows 7 Beta/RC. I have had really good success with MSSE finding/blocking security threats. Also, so far, the performance of MSSE has been pretty good as well:
CPU usage is typically @ 0% active
RAM sits around 32MB
And blogs are starting to review and report that the MSSE product is scoring very well in the “Free Options for AV” niche.
PCMag.com
190 points and 3 stars
http://blogs.pcmag.com/securitywatch/2009/12/av-comparatives_rates_anti-mal.php
