Ok
Let's work out the mechanics.
As I understand it, you made a casper copy using a new drive.
Then you took that casper copy and replaced the original drive and you now have the Casper copy as your primary C drive and are attempting to use the original drive for new Casper copies. Am I correct so far?
Basic questions:
Is the new D drive an external drive or is in inside the machine?
If it is inside, did you switch the master/slave jumpers?
If it is external, did you format and try to make a new Casper copy out of it. Or are you attenpting to fool Casper into thinking the original is now the copy?
I would think that Casper is choking on the switch and you need to format the D again and re-ghost it so Casper doesn't get confused.
As for the three Gig difference, I would think that is a difference of fragmented and temp files plus the Casper program.
I have never done what you are trying to do and am wondering, why, all things being equal, you are doing it in the first place.
BWTFDIK
BT