I have one word of caution about the freeware programs. If you don't keep your system current, they sometimes stop supporting the older operating systems. This happened to us a few years ago with Windows ME on an old computer.
Currently I don't use a free one, I keep up the subscription with Norton and have not had any problems in 4+ years (knock on wood). Since opting to pay for the service, I have NOT had to restore my computer at any time in those 4+ years. But I had to on my previous computer where I was using the freeware.