Int 2F Fn 1100  C - Network Redirector - Installation Check                [N]

   AX = 1100h

Return: AL = status
       00h not installed, OK to install
       01h not installed, not OK to install
       FFh installed
       AH = product identifier (ad hoc by various manufacturers)
           00h if PC Tools v8 DRIVEMAP
           42h ('B') for Beame&Whiteside BWNFS v3.0a
           6Eh ('n') for NetWare Lite v1.1 CLIENT

Notes: this function is called by the DOS 3.1+ kernel
   in DOS 4.x only, the 11xx calls are all in IFSFUNC.EXE, not in the
     PC LAN Program redirector; DOS 5+ moves the calls back into the
     redirector
   the PC Network 1.00 redirector (renamed to PC LAN Program in 1.1-1.3)
     only supports AL=00h-27h