Logical Volume Manager
Local device drive names (each of which is a letter of the alphabet) are usually assigned incrementally, starting with the letter C (C, D, E, and so on). Network drive names are automatically assigned in reverse order, starting with Z (Z, Y, X, and so on).
Conflicts between drive letters and existing network shared drives can arise if you connect digital cameras or other devices that use memory sticks to Windows XP while the computer is running. Similar conflicts can arise if you add external drives (such as USB or 1394 disks). If a naming conflict arises with an existing network shared drive, the device or external drive becomes inaccessible.
To prevent this problem, allow Windows to automatically assign network drive names, or choose letters higher in the alphabet for your drive names.