BOAC,
If you clone your C: drive to the 20GB disk with Ghost you can either leave it as a 4GB partition (leaving 16GB for a new partition - G: or whatever) or expand it to 20 - Ghost will manage this, I believe (I've only ever used Ghost to clone disks the same size, single partition). I assume that the version of Ghost you have supports W2K.
You would then leave the other existing disks exactly as they are. No need for a new install of W2K, you would continue to use the install you have got.
Making the D: drive a bootable disk for W2K is done during the installation of W2K. Forget 95/98.
SD