This is as good a place as any, since there's not a dedicated forum related to Security/Virus Protection as opposed to helping with problems once they're there.
I will repeat what I've often said elsewhere: Your own "browsing, download, and jump drive hygiene" are far more critical in protecting you from threats, be they malware, viruses, worms, or what have you. Most infections are the direct result of bad decisions as far as clicking links from unknown sources, plugging in jump drives where you have absolutely no idea where they've been, or the like.
Most current antivirus programs do on-demand scanning of e-mail (if you're using a client to download it as opposed to a web-based interface, which doesn't need the same sort of checking) and downloaded files. Many, though not all, can be set up to scan any USB drive that is inserted before it is available for access.
I'm currently using Windows Defender, which comes with Windows, but have used Avast!, AVG, Panda Cloud Antivirus, Clamwin with Clam Sentinel, and others and I don't really feel that any was "head and shoulders" above the other. I've had less than 10 possibly infected e-mail messages and downloaded files over the course of several decades. I'm all over the place on the web, but "the reputable" parts of the web.
You might also want to take a look at the Bleeping Computer forums, specifically the one on Anti-Virus, Anti-Malware, and Privacy Software. There will be people there who will say that what I've said above is crazy (at least the part about Windows Defender being OK), but at least then you'll have a variety of viewpoints presented and can make a decision you'll be comfortable with.
Edited by britechguy, 29 December 2015 - 05:38 PM.