Personally I only use Microsoft Security Essentials. I only need and want a file antivirus. I have no need for a firewall (A router is a hardware based firewall) or any of the other bloat to make me feel protected.
No antivirus is perfect and so I refuse to pay for one lol. Not to mention MS has way less false positives than any other. Other techs or people will say you need something better, no you dont. But then again if your not behind a router and wide open to the net then you will want firewall software, otherwise, since I am behind a router and I dont need to block any programs the windows firewall does fine.
I havent been infected in over 6 years.
There are a lot of free antiviruses out there, all of them will try to make money somehow, either by installing toolbars or trying to get you to install 3rd party apps or bug you to buy their upgraded versions. MS is the only one who doesnt do that.
But everyone has their fav. so if you do then stick with it. If you check
http://www.av-comparatives.org/ you can get an idea of one you will want to try.
You will see Norton and a lot of the big names have a huge amount of false positives.
As for making a donation I have a link on the menu on the left on my main site tweaking.com
Shane