Thanks Selden - I'll have a look at that
I have Avast (cheapest purchase version), but I uninstalled it because it was being a pain in the B with constant 'buy the more expensive version of me' advert popups!
It also never saw something that Defender caught trying to get onto my system a couple of weeks ago
I've done the update. Everything seems to be fine on the Windows partition atm (I'm on it now), but I don't generally use my machine for games an awful lot, which is what I understand is causing the problems? Not entirely sure.
I can breathe again for now - until the next update.
Windows is merely storing my data and running the apps I can't move over to Mint for now, but it would still be a pretty big blow if I lost Win 10 functionality any more than it already is at this early stage of crossing over to the 'dark side'
EDIT: spoke too soon. The newest update to Win 10 does something disastrous to the browser. Edge isn't working at all, and Firefox is very slow, so I'm back on Mint again now.