Int 21 Fn 4B53  - Virus - "one Half" - Installation Check                  [v]

   AX = 4B53h
   BX = 2121h
   CX = 1212h
   DX = 0236h

Return: AX = 454Bh if installed

See Also: AX=4B50h,AX=4B53h,AX=4B55h