Silly me. It's over four hours later and still scanning. (I think it's also scanning my back-up drive, which is what's made it seem SO long.) And since this is all before Windows has loaded, I can't use the computer, while simply scanning in the background.
Then, feeling like a fool, so focused on my desktop system running through its scan, I realized that I actually have a notebook computer, sitting off there elsewhere at home.
So, I've started that up, and here we are...