How did you determine which motherboard I had?
Anyway, I reloaded the drivers from the motherboard disc by running the install facility, but it made no difference.
However, updating the driver via Device Manager worked by pointing the updater to the motherboard disc. This set up everything except ...
It told me the USB keyboard is unplugged, which is arrant nonsense as both the keyboard and mouse are plugged in.
I have two computers with a KVM which switches the keyboard and mouse (not the video) between the XP and Win-7 machines, but I could only access the Win-7 machine via MS's Mouse Without Borders, which is fine as far as it goes, but there is was no access to the Win-7 machine via the KVM.
The problem was eventually fixed by swapping over the keyboard and mouse connectors on the Win-7 side.
Solved. Thank you both for your time.