I am going to mark this thread as closed, even though the problem itself has yet to be completely solved. My first attempt at creating a new Windows profile ended up with a corrupt document; I don't know how that happened, it might have been my floundering about.

I created a second new profile, where I quickly found some problems. For example, the email program Thunderbird, in User\John\App Data\Roaming, should have had a folder, Profiles, and below that, a text file, profiles.ini. These are used to allow Thunderbird users to have multiple profiles, and to choose between them. Instead, the Windows profile creation process extracted two profiles from the folder in my default Windows profile, and put them where the folder should be, and did not transfer the text file. There is a tutorial on moving Thunderbird profiles; I will use that to correct the Windows profile problem. The Firefox web browser has a similar, but less serious problem, but one that does need to be corrected.

Those are the most serious things I have found; some of the others were quickly fixed. Given the amount of time this process has taken, I have decided to just keep the new profile, rather than creating yet another profile when I make this one the default. I don't have to have "John" appear on the lock screen, after all.

So, again, please accept my thanks for your assistance with something that otherwise might never have been undertaken.