I'm back, sorry for the delay in providing a response. No I don't have any card readers attached to my pc.
The comment by pete.i. was interesting where he said "providing all the available drives were deleted at the point of initial install ( which is what I would do with a clean install) then there shouldn't be any hidden drives" Not exactly being a whizz with computers, I don't know what he means by this as when I did the clean install I don't recall anything popping up about the hard drives.
Over the weekend I'm going to try allocating drive letters that are available and will then try to change them again afterwards, as suggested by BikerEcho.
pete.i. also suggested that these drives might be hidden Is there some way of checking this?
Thanks again for all the help.