Last Updated Jun 28, 2009 10:19 PM EDT
As a long-time user of AVG Free, I have been pleasantly surprised by Security Essentials. The program does all the stuff you'd expect -- like allow you to schedule regular system scans, perform real-time scans, and optionally specify locations and file types to exclude from the scans. PC World reports that Security Essentials has a tiny footprint and had little impact on system performance, and I can anecdotally confirm that myself. If your PC is not already managed with anti-virus software, give this one a shot.
Dave Johnson was employed by Microsoft Corporation at the time this article was written.