INT 2A - PC/TCP PREDIR.EXE - INSTALLATION CHECK
        AX = FF92h
Return: AX = 0000h if installed
           BX = redirected printer port (FFFFh if no printers redirected)
           CX = version (CH = major, CL = minor)
Note:   PREDIR.EXE is the network printer redirector included as part of the
          PC/TCP system by FTP Software, Inc.