I've used AVG free version for years, and I think it's good.
A big improvement for me was switching to Mozilla Firefox as my browser, instead of using Internet Explorer. Alot of the viruses and spyware are targeted at Internet Explorer, and they don't get into Firefox . Just using Firefox lowers your chances of infection, and Firefox is a great browser. The multiple tab browsing selection is a great feature, and I like Firefox alot more than IE.
I have some computer geek friends that use Linux. They like it, but they all tell me that it's more for computer-savvy type people, and there are some things that you have to work around, and some things don't work with it. They are all software engineers, so it's no big deal for them.
So, that's why I haven't gone there.