Drive letters are assigned in each OS and are not shared or ordered by any single OS. You MAY NOT change the OS drive letter without deep registry editing and the work is so involved that the answer is "no" and "don't do that".
Non-OS drive letters can change. But what you want is not going to happen without consequences. The best you can hope for is the data drive to be the same letter.
I have two copies of XP installed, one will be stripped down for audio use (Audio OS), and one for general use (General OS). When I boot from the boot manager list into my audio OS, and go to disk management, the drives are setup as I expect:-
C: Audio OS D: General OS E-L My other partitions
When I log into my general OS, the drive letters are muddled:-
C: Audio OS L: General OS Other Drives: not in order
Here, I expected General OS to be on C: (as I am booted into it) and the Audio OS on D: Would this be right? How do I go about swapping L: to C: and C: to D: without causing boot problems?
I have already tried this once by changing the names in the registry
(HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices) but this went wrong and wouldn't allow me to boot into the general OS anymore.
I am now back to the stage where I was before it went wrong and am really nervous to change anything!
Some guidance would be really appreciated