no wiser, but not so sad
Thank you for your suggestions. I can report that in the 3 days since posting the original query, and while waiting to see if a TRIVIALLY EASY solution might appear, the problem has fixed itself. I can only speculate that some unknown update detected and fixed the...
On my laptop screen there has suddenly appeared a 'blank' window, associated with a tab that, when opened, identifies as
"Intel Services Manager
Pin this program to taskbar
Close window"
Nothing I do will remove the tab or the window. The problem persists through a power-off/restart cycle...