I switched from AVG to AVAST a year ago. Much better IMO.
http://www.avast.com/eng/download-avast-home.html
And written by competent folks from Vaclav Klaus’s country-the Czech Republic!
I’ve used AVAST free addition for several years and haven’t had a problem.
Before that...I had Symantec and was re-installing windows every 6 or so months. Drove me nuts!
We have AVAST on 4 home computers now and they all, are doing well. And I do use FIREFOX.
But I even used that during the Symantec mess.
Anyway... we had to have Norton Symantec un-installed on my husband’s laptop at the store where we purchased it, simply because we couldn’t.