Malware Bytes is amazing. I think the only main difference between the free and full version is that the free version your have to tell it to run scans (which is important), whereas the full version you can schedule the scans.

Norton and McAfee are horrible. Be careful while uninstalling Norton, sometimes even when you think you uninstalled it it is still there. (which makes putting another AV/AS on your computer I think there are actually free software downloads out there specifically to remove Notron.