People never believe me but I haven't used AV software for the last 10 years...it's useless, unless you're doing "dodgy" things with your PC that you know you shouldn't be. You're more likely to get something from browsing the 'net these days...in which case, I advocate using a Linux distro to do.
AV software ratings change every year and none of them are foolproof. Both Norton and McAfee have become lessons in how to design bloatware and "Free" just isn't what it used to be compared to the mid-late 90's as far as software goes. I typically recommend NOD32 to family members if you feel like going down the subscription route.
Here's a link to the 30-Day trial if you feel like giving it a go:
(Urgh...I haven't made more than 10 posts yet so I can't include a URL. Just Google NOD32, it'll be the first link in the list. I'm sure you can find the trial from there.)