Getting a drive letter to "stick"

I have an external 2TB WD that I use to copy files to.  It needs the drive designation to be Z:  When I plug it in, Windows Server assigns it G:  I go to manage my computer and reassign it to Z:  When I disconnect and  reconnect it is back to G:<o:p></o:p>

Suggestions?<o:p></o:p>

Thanks<o:p></o:p>