The solution is really simple (although not that optimal): in
Vista/Windows 7 you assign the drive letter back to the volume, then it
will automagically be available in XP and have that drive letter.
This has happened to me on an XP/Windows 7 RC dual boot installation.
And I've searched the internet for days to find a solution, without
success. I had not realized that removing the drive letter had caused me
the problems until I came by your post, so thank you and thank you again
(as my spanned volume is 650Mb in size and it would require a couple of
new disks and ages to back up).
--
SeventhUser