Tried the HDD copy again - it failed to boot again. The complaint was that something like Winload.exe was corrupted...

So I put in the Paragon system recovery disc and found the drive letters were again D: and G: and corrected them to C: and E: - Reboot - fail.

So out of desperation I ran every boot fixing thing on the CD - Fix MBR and a couple of others. I rebooted.

It now works

I fixed it, I'm just not sure how or why it wasn't working, or which thing I did was the one that fixed it. I was hoping to learn from the experience, but the only lesson I learned was "try everything and hope" - I knew that one already.