I've been using Avira, another of Veks' freebie recommendations, and pretty much always satisfied with it.
It doesn't nag a lot about dropped connections or a little time away, in the way that some programs do. Most of the time, I barely notice it's there. But I haven't seen a great deal getting through, either. And the few times I've suspected real trouble, it has picked stuff up on the active search and dealt with it. It also gets stuff done without having to search your whole
computer (or even worse, having to finish
the full machine search in one go), which some still do not.