Int 2F Fn B800  - Network - Installation Check                             [N]

   AX = B800h

Return: AL = status
       00h     not installed
       nonzero installed
         BX = installed component flags (test in this order!)
          bit 6   server
          bit 2   messenger
          bit 7   receiver
          bit 3   redirector
          bit 1   LANPUP (LANtastic 4.0)

Notes: this function is supported by LAN Manager, LANtastic, NetWare Lite,
     SilverNET, 10NET, etc.
   LANtastic and NetWare Lite use only BL for the return value, preserving
     BH; LAN Manager and DOS LAN Requester return BH=00h.  This permits
     differentiation between those two groups by setting BH to a nonzero
     value before the call and checking its value on return.

See Also: AX=4E53h,AX=B809h