INT 33 - Mouse Systems MOUSE DRIVER - POPUP.COM - INSTALLATION CHECK
        AX = 0070h
        BX = ABCDh
Return: AX = ABCDh if installed
            BX:CX -> data structure (see below)
Notes:  this function is also supported by the Genius Mouse 9.06 driver
        the v7.01 POPUP.COM and menu drivers also check for the signature
          CDh ABh BAh DCh at offset -2Ch from the interrupt handler
        if POPUP is not loaded, the returned data structure contains the proper
          signature at offset 00h, but not at offset 08h

Format of data structure:
Offset  Size    Description
 00h    WORD    signature ABCDh
 02h    DWORD   pointer to info structure???
 06h  2 BYTEs   ???
 08h    WORD    signature ABCDh

Format of info structure:
Offset  Size    Description
 00h    WORD    driver version
 02h  8 BYTEs   ???
 0Ah    WORD    segment of ???
        ???

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