Many thanks for your prompt and detailed reply.

It is very interesting and has taught me a lot.

Shortly before i accessed it, somehow the external hard drive icon turned up in the One Drive folder (how this happened beats me !). I dragged the icon to the desktop, and, wonder of wonders, all was back to normal again.

The fascination of modern technology, or what ? No wonder I am still learning computer navigation ever since I started back in 2003...

Once again, thank you, thank you very much, and best regards.

Joe