When you create or mount a dynamic volume in Windows Server 2003, you must explicitly assign a drive letter to the volume, as they are not automatically assigned.
This behavior occurs because the NO_DRIVELETTER volume attribute is set to Yes on all dynamic volumes, because the NoAutoMount Value Name does not affect dynamic volumes.
You cannot alter the NO_DRIVELETTER volume attribute
NOTE: If dynamic volumes were auto-mounted, technologies such as SANs (Storage Area Networks) would not operate correctly.
To assign a drive letter, use the Disk Management snap-in or the DISKPART command.