SD - thanks for that reply - I had feared it was as complicated! I had tried copying all the root files from 'C' to 'D' but that did not help!
It does sound as if a fresh install on the new 'C' drive (with all its associated woes) is the best solution. Then I will work out how to swap the drives around (I have 'ghost').
ONE(!) of the things I do not understand is how I could make the existing 'D' drive a system disk. In 95/98 it was a case of 'sys d:' I believe, but I have a feeling that my 'sys.com' file is the 98 version (having upgraded) and therefore the wrong MS OS for W2000?