I don't think the windows 8 built in antivirus slows me down at all since I haven't had a single millisecond of slowdown this shit is fucking unreal
I have malwarebytes and superantispyware how often should I scan with them? I always forget because you gotta do it manually unless you buy them and I only go here and fjs and I'm gonna stop going here because this place is a virus so I'll just be going to fjs and secondlife.com
pretty much whenever you think you're infected, you could set it on a schedule but it's probably overkill if you're not some numbnuts who installs every toolbar and looks at porn without adblock