I'm sure better advice will come along soon, but I would think, at first glance, that your problem is going to be changing the "C:" drive from one disk to another? I would have thought that the Windows HAL will throw a wobbly
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Why not, for simplicity, just install XP on the 74GB drive ("I:")?
Leave W2k on "C:" and, if you wish, set the system up to dual-boot W2k or XP.
Unless there is a particular reason for wanting to swap the "C:" drives around I would leave them alone. As long as the DOS system is on "C:" plus the "boot.ini" I would think you'll be OK.