Int 2F Fn CB00  - Mtez Xpressfax Casmgr - Installation Check               [F]

   AX = CB00h
   BX = 4D53h
   CX = 4949h

Return: AL = status
       00h not installed, OK to install
       01h not installed, not OK to install
       FFh installed
       BX = 6D73h
       CX = 6969h

Note:  this function is equivalent to the standard CASMGR installation check,
     but uses the additional magic values to identify which CAS is
     installed

See Also: AH=2Ah,AX=8000h"FaxBIOS",AX=C000h"MTEZ",AX=CB0Eh,AX=CB16h