In round 1, my Start Menu had been reset to the default, my wallpaper was missing, and none of my files were accessible.
Then the machine crashed out when I tried to log out.
Round 2: I log in and am given the "Hi. Your computer has been updated. All of your files are where they used to be." message. Miraculously, the files are there when this nonsense abates and I am allowed to log in. My wallpaper was still missing. I am run through the procedure to establish a Microsoft One Drive which I don't intend to use, but which I figure I will let it do to get it to shut up. And when I tried to go to the Start Menu, it crashed and I got a message telling me to log out to reload it.
Round 3: So I log back in. Now I have my correct Start menu back and can access my files. I pull up my email and try to display one of the mails in my default browser, Google Chrome.
The email displays in Microsoft Edge.
I fire up Google Chrome. It says that it is still my default browser.
Apparently, "default browser" does not mean what you think it does, grasshopper...