I should, of course, have known better, but, running ahead of the deadline, I "upgraded" to Windows 10. (I *did*, at least, do some research before I started, and turned off the worst of the privacy issues.)
I ran smack into the intermittently reported problem of intermittent Internet connection problems. Some sites I can reach, others I cannot. Some sites I can reach sometimes, and not at others.
Yes, I have tried Google, thanks. I can reach Google (most of the time). Unfortunately, an extremely high proportion of the sites purporting to have answers are among those I cannot reach. (Including, interestingly, answers.microsoft.com.)
Yes, I guess I did leave out rather a lot in that bit, did I not? I was getting a bit frustrated at that point.
I actually upgraded two machines, the desktop from Win 7 Pro, and a laptop from Win 8.1. (This means one machine runs Win 10, and the other Win 10 Pro. There are differences.) Both have SSD drives as C:/boot. The laptop is connected to the router via ethernet, and the laptop via wifi. The ISP is Shaw.
Retrying various sites I did, eventually, get through to a Microsoft page. I had to bounce around in their system a bit, but eventually got to:
A lot of the suggestions are simplistic, or otherwise unhelpful. But, about halfway down the page, it gets into networking commands. Apparently Win-R is not good enough anymore. You have to use "the search box on the taskbar"--that is, Cortana. "type Command prompt, right-click (or press and hold) Command prompt, and then select Run as administrator > Yes."
Type netsh winsock reset and press Enter.
Type netsh int ip reset and press Enter.
Type ipconfig /release and press Enter.
Type ipconfig /renew and press Enter.
Type ipconfig /flushdns and press Enter.
So far that seems to have fixed most problems, but some issues remain. But intermittently. (Argh.)
The Microsoft suggested network resets do work, but don't seem to work for long. At the moment, the connection seems to degrade over several hours (as well as having intermittent sites that aren't reachable on a sporadic basis). Doing the network resets again seems to (mostly) rectify the situation. I'm wondering if I am going to have to put the reset package into a batch file. And possibly reboot the computer every day. Or maybe more often. (I got a suggestion about using Win-X to get an admin command prompt: very useful.)
Any and all suggestions gratefully received. (Except "upgrade to Linux." There are reasons I can't. I am hoping not to have to revert to Win 7.)