Okay, after a little bit of research, I've figured out what the problem is. . . .
This particular update is a "patch update" that's supposed to work as a "compatibility update," meaning it's Microsoft's way of trying to put PCs still running Windows 7 or 8 into something of a transitional mode to prepare them for 10.
https://www.computerworld.com/artic...6978-2977759-and-windows-journal-3170735.html
It's ironic how I've read so many blogs and articles that are like, "I upgraded my version of Windows, and was so relieved that nothing went missing during the update. I left some programs and windows open just to see, and they were just as I left them." Yeah, again, this particular update is almost like a factory resetting, because almost everything is wiped out. Both times this has happened, all of my personal files, folders, and such were completely gone; but the first time it happened, at least my wallpaper hadn't been changed, though I had no internet access (not even IE), and some of my Adobe programs were still installed; this time, I still had all of my installed browsers (IE, Opera, and Chrome), but even the wallpaper was reset, and all of my installed programs were gone.
Granted, I'm actually able to back things up now, so it's not like it would be a total loss: things like Audacity, Spybot, and VLC Player are free, so I could easily re-install them; likewise, I have Adobe's Creative Cloud service, so it would be just as easy to re-install those programs, and basically re-import files and folders I've backed up . . . but why would I want to basically redo everything on my computer as it was before? Right down to recreating my saved themes/resolution/layout/etc. all over again? Again, I'm lucky enough all I've had to do it do a System Restore and boom, everything's back to normal. But this is exactly why on my old computer (which ran XP), I
wouldn't update, because I
couldn't back anything up - certainly not the programs I was using since at the time, I didn't have Creative Cloud, and all of the now-Adobe programs I had installed were done so from a loaner installation CD back when many of those programs were owned by Macromedia.
But yeah, I'm just keeping Windows Update turned off at this point.