Was nothing wrong with the drive or the setup disks. It was finger trouble.
The choices I had when I started the program were to diagnose the system, a button to click and a description of what it did, and another button to reformat and set up the original programs on the C drive, including an explanation of what would happen, which I pressed and got nowhere, because the drive letter was not found.
And a small check box labeled "skip" with no explanation.
So I skipped, and the program ran, reformating and loading all that my tiny little shrivelled heart could desire.
I hate computers.