Int 2F Fn 5712  U - Iomega Drivers - Unlock Media In Drive / Eject         [d]

   AX = 5712h
   BX = program ID??? (0201h used by GUEST.EXE)
   DX = 496Fh ('Io')

Return: AX = new lock count (00h = unlocked)

Note:  if the lock count was already zero, the storage medium is ejected
     from the drive

See Also: AX=5700h,AX=5701h,AX=5710h,AX=5711h