THanks for that Michel. I have been unable to stop PSE extracting the photos to the old drive whose serial number it likes, short of temporarily disconnecting that drive!
HOwever, I am managing to work around my problem, although it is a tedious process with such a large catalog. I am using the feature in PSE which allows us to move files or folders from within the aorganiser. Thst way, I should end up with everything on my D:\ drive as wanted. Had a couple of glitches but am getting round them at last.