INT 2F - WINX - RETURN ADDRESS OF SERVER BUFFER
        AX = F201h
Return: AX = FFFFh if WINX is busy processing a different request
           = 0000h if successful
            BX:CX = address of server buffer

Format of server buffer
Offset  Size    Description
 00h    BYTE    command/status
                00h buffer available
                01h buffer contains result
                02h change directory
                03h execute program
                FFh terminate windows portion of WINX
 01h  ? BYTEs   command (03h) or directory (02h)
  or
 01h    DWORD   result (01h)

.