Whenever we connect a drive whether new or the earlier connected, Windows assign it a unique Drive Letter randomly. Managing these letters is possible in Windows through diskmgmt.msc but only for the connected drives.
In order to change/remove drive letters on Windows 7/2008/Vista, you have to right-click on DriveLetterView.exe and choose ‘Run As Administrator‘. If you run it without admin rights, DriveLetterView can display the list of all drives, but you won’t be able to change/remove a drive letter.