I don't know if this will be any help to you..
To change or swap drive letters on volumes that cannot otherwise be changed using the Disk Management snap-in, use the following steps.
NOTE: In these steps, drive D refers to the (wrong) drive letter assigned to a volume, and drive C refers to the (new) drive letter you want to change to, or to assign to the volume.
This procedure swaps drive letters for drives C and D. If you do not need to swap drive letters, simply name the \DosDevice\letter: value to any new drive letter not in use.
Changing the System/Boot Drive Letter
Make a full system backup of the computer and system state.
Log on as an Administrator.
Start Regedt32.exe.
Go to the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
Click MountedDevices.
On the Security menu, click Permissions.
Check to make sure Administrators have full control. Change this back when you are finished with these steps.
Quit Regedt32.exe, and then start Regedit.exe.
Go to the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
Find the drive letter you want to change to (new). Look for "\DosDevices\C:".
Right-click \DosDevices\C:, and then click Rename.
NOTE: You must use Regedit instead of Regedt32 to rename this registry key.
Rename it to an unused drive letter "\DosDevices\Z:". (This will free up drive letter C: to be used later.)
Find the drive letter you want changed. Look for "\DosDevices\D:".
Right-click \DosDevices\D:, and then click Rename.
Rename it to the appropriate (new) drive letter "\DosDevices\C:".
Click the value for \DosDevices\Z:, click Rename, and then name it back to "\DosDevices\D:".
Quit Regedit, and then start Regedt32.
Change the permissions back to the previous setting for Administrators (this should probably be Read Only).
Restart the computer.