I've noticed that recently Avast free antivirus is getting much more aggressive with the popups, they're being shown on every boot now. I've got my whole family on it, and they're starting to complain. Anyone worked out how to reduce them?

Can anyone recommend free antivirus that does a good job and isn't too intrusive? Don't say Microsoft, I read reports a while back and it's generally at the back of the pack for detection. The primary user will be computer illiterate users - think parents or grandparents to whom computers are a confusing tool, a way to access the internet and email.