Int 21 Fn 5F07  - Dos 5+ - Enable Drive                                    [D]

   AX = 5F07h
   DL = drive number (0=A:)

Return: CF clear if successful
   CF set on error
       AX = error code (0Fh) (see #1366 at AH=59h/BX=0000h)

Notes: simply sets the "valid" bit in the drive's CDS
   this function is not supported by Novell DOS 7 through at least
     Update 4, but support was added by Update 13

See Also: AH=52h,AX=5F08h"DOS"