Avast as a lot of people said is probably the best for free antivirus software. I've used just about everything and I find that Avast has worked the best for me. I also like Norton but I feel like its just not as good as Avast. I've ran a scans on Norton and its come up with nothing. Just after I would run a scan with Avast and a few things would pop up. So I would say Avast is the best free antivirus software.