It may be that those backup files live somewhere else for some reason... Open Explorer, select "C:" and search for ".wbk" (without the quotes). wbk is the extension Word uses for those backup files. Let search run and finish then delete *all* of the files it finds with that extension. It's likely they'll be in "My Documents" but searching "C:" should find them if they're in another unexpected location.There were maybe a half dozen files which I deleted. I no longer get the MS Word dialogue box, BUT the multiple file openings with freeze up, followed by eventual MS Word crashing bugaboo remains!
If that doesn't work, you *may* need a full, complete, uninstall of Office. To do that:
Run the Office uninstaller and reboot when it finishes.
When the computer is back up, open Explorer, browse to and delete *all* folders that have "Microsoft Office" as the name or part of the name in "C:\Program Files". Do the same in "C:\Program Files (x86)".
Browse to "C:\Program Files\Common Files\microsoft shared" and delete any folders which have OFFICE as the name or part of the name (leave all others). Do the same in "C:\Program Files (x86)\Common Files\Microsoft Shared".
Browse to C:\Users\[username]\AppData\Local\Microsoft" and delete the Office folder (leave all others.
*Finally,* go to "C:\Users\[username]\AppData\Roaming\Microsoft" and delete folders having a MS Office name (Office, Word, Excel, PowerPoint, Access, etc.) *and* the "Templates" folder. Do *not* delete any other non-Office folders (You'll likely see folders for Edge, and other MS apps and should leave those alone).
Once you've done that clean up process, reboot. Then install Office again.