So on that copy of the "standard set up" I posted up there, would that suggestion you made Jon mean I should change the setting under "mode" for the Secondary Master from "LBA" to "Auto"? Or what?

I want to get it back to how it was before, even if some other way of doing it would be better in theory. As I said, the two drives were working fine before I had to reinstall windows because of the problem with the registry. (Or rather, because the man on the helpline said it needed to be done as the only way of getting back my cursor, indicating that "your registry is corrupted" which sounds very unpleasant).

And the only thing I moved was that litle plastic plug with the multi-coloured wires which I pulled out before reinstalling windows, and later replaced (or maybe I replaced it with the identical one hanging next to it). All the jumpers and the ribbon cables and so forth have not been touched.