I tried all sorts of things to move the offending files down the hill a bit. I think Bush suggested what was causing the problem, but nothing I dared do would budge them.
Using XP was the answer, but as I said, it was a radical solution. However, the files on D and E were shuttled about, enabling me to format each drive in turn without resorting to backup DVDs.
One thing that was a happy byproduct of all this was the resolution of a very tedious problem with the elaborate sound card (On the MB.) The Full format must have removed some detritus from the C drive. From that time on, the bewilderingly elusive fault on the audio, just disappeared, and this was after reloading the drivers scores of times and trying MS and the maker's software turn about turn.
Just goes to show how important starting with a clean sheet of paper can be sometimes.