I spoke with the OEM who, fortunately are still in business, willing to be helpful, and knowledgeable. They gave me a link to http://www.microsoft.com/office/downloads/ from which a slightly different download was possible once I entered the product key. Now the thing activates just fine. Kudos to PC Specialist Ltd.

Incidentally, I had chat sessions with M$ support on two occasions. They gave me two different answers both of which ended up in buying the product again being the best way forward. Anti-kudos to M$.