Just stirring the pot a bit... On Windows-8 there is no more MSE (Microsoft Security Essentials). It's integrated into Windows Defender so what that means is that with a Windows-8 PC you don't need any additional antivirus at all because the best you can get is already included (and it forces you to auto-update).
http://windows.microsoft.com/is-IS/windows-vista/Turn-Windows-Defender-on-or-off a little google goes a long way
Best antivirus is to have system and procedures that do not need one, and to have systems that need antivirus running disposable software/data/hardware. .
The best philosophy is to view oneself as disposable... And carry cyanide capsules in case anything goes wrong.
Family XP computer with MSE got infected with System Progressive Security, installed itself, disabled MSE changed registry etc. Bravo! So why do I have warnings trying to install programs or access certain folders and functions and viruses get free pass to my computer. So the only advantage of MSE (Microsoft) is that it does not slow your computer and easily integrates into Windows as opposed to competition but seems to be useless.