I was having slowdown issues with a computer (Vista 32-bit os) which had not been started for about a year and had no av installed, but still a pretty good computer (Lenovo Ideapad Y510). I started trying several av's for which I had licenses. I first tried AVG internet security, but it did not load. Then I tried the new Trend Micro internet security. It too did not load (I remember the error code, #1603). Then I tried Roboscan Pro, which did not load. Then I tried Norton internet security, and it did not load. I had one more program, McAfee Total Security. Before it started loading it said that it would need to clean up the computer, and it spent about 30 minutes scanning. But after the scan it came through and loaded. I guess this was a heavily infested system which only McAfee was able to defeat. Quite impressive, but of course with only a limited sample of five av's. But I thought I'd share my experience.