In reply to Sam Beaton:
A couple things:
If you're not using AV, which is fine, make sure you at least have a decently protected browser. Don't use IE, preferably Firefox with Noscript/Adblock+, in a pinch Chrome will do.
Windows Defender is balls. May as well turn that off. As for scans, Iobit is similarly balls and you don't want to rely on it. Malwarebytes should be used as a replacement, since it's built with weekly scans in mind whereas IASC is a multiuse tool and tries (and fails) to be the jack of all trades.
As for Windows Updates, turn them off and forget about them. They do more harm than good and you'll never be able to attribute a problem with the system in terms of malware/viruses to not having installed updates. As long as you're not using IE, that is.
My 2p, anyway. I run my machines without antivi and have done for over a decade.