I am a computer repair tech, and I have had to follow up on vitually every major Security/AntiVirus software made. I seldom have any security problems with systems protected by Avast. Since its demands on system resources are much lighter than most others, and it catches more viruses than anything else I have used, I prefer it to any other software of it's kind, free or otherwise. Well done, Avast! (By the way, the interface is excellent.)