And I must defer to all those prior discussions. I think that the free version is far better than none. And if you feel like an antivirus is good, why not pay up.
However if a free version installs some adware then I'd uninstall and try another. Be aware that Download.com appears to still be bundling in software most of all never want so avoid that site.
Bleepingcomputer.com should have links to WOT and Adblock+ if you fail to find such with google.
What advantage does AVG or Avast have? They offer us a choice in free antivirus. That sounds like I'm dodging the question but let's face it, if either didn't work, you would have read about it.
Bob