INT 2F U - Quarterdeck - MANIFEST v1.0+ - INSTALLATION CHECK
        AX = D201h
        BX = 4D41h ("MA")
        CX = 4E49h ("NI")
        DX = 4645h ("FE")
Return: BX = 5354h ("ST")
Note:   QEMM/QRAM/VIDRAM/MANIFEST will search for a free AH value from D2h
          through FFh, then C0h through D1h