Well .......
I was on Windows 7. I had downloaded Windows 10 but not installed it.
I had a message saying "we are going to upgrade you on Wednesday 9th March at 23:00 whether you like it or not." Seriously. If you get a similar message, you'll need to take steps to stop it doing so.
(I've had an icon with 4 white windows on my taskbar once I'd downloaded it back last Autumn, and it was only by clicking on that that I got the warning of impending upgrade message. IIRC, on that message pop-up, there was an option to cancel or postpone the upgrade.)
But I decided to take the plunge and upgrade this evening. Took about an hour. (We bought a laptop for Mrs O with W10 in January so I am slightly, but not hugely, familiar with it).
Seemed OK .... but then the TP Link internet connection went down - terminally!
It's the Wifi antenna attached to the PC and it's been playing up for a bit, TBH.
So I have just shot down to Asda as I know they do TP Link products and bought a Powerline Adapter - a pair of thingummys whereby you connect one from your router and plug it into the mains electric circuit, and the other into a socket near your PC and connect that by cable to the said PC - and it routes your broadband connection that way through your electricity circuit cable, rather than by wifi. We connect the laptop up in that way, and the PC now seems to be working OK as well.
Fingers crossed.
You're probably all using these anyway and I'm only just catching up with the 21st century ...