I have now pulled the plug on everything but the main drive in the hope that the system would re-assign...but it didn't.
I had thought I would have to do what you say, but what about the drive with the install disc? That is the one that in fact grabbed C:
D: was the CD drive after and numerous card readers, now disabled, took letters up to H: and at this time they boot/system is on I:
I'll get rid of the logical drives on the next install, but as I say, I seem to be stuck with the DVD startup. Incidentally, that's the only other boot drive offered in the BIOS