bocadillo
Water Gypsy
When you had a D drive what was it? On my dell it is the CD/DVD Drive so the best bet is that computer doesn't recognise that at the moment. Do you still have access to the CD/DVD? Can you put a CD into the drive and can the computer read it? Best to start there.
That's a strange conclusion to draw.
If the OP can't tell us what kind of a drive has been 'lost', perhaps it was never there at all.