Vista RC1 Dirve Letters?!

hello,

my partitions in xp look like the following:

c: windows xp (installed)
d: empty
e: vista (empty yet)

then I installed Vista RC1 x86 (new install to e and all drive letters
changed in vista to the followings:

c: vista
d: windows xp
e: empty

any idea how to change the drive letters in vista? i want to have the
same drive letters in win vista like i have them in win xp, but vista
changed them while installing and i cannot undo that action. i tried it
with the disk management, but without success: access denied!

thanks!