Int 2F/AX=5712h

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