INT 21 - LANtastic - GET INACTIVE SERVER ENTRY
        AX = 5F84h
        BX = server index not currently logged into
        ES:DI -> 16-byte buffer for server name which is available for logging
                in to ("\\" prefix omitted)
Return: CF clear if successful
            DL = adapter number to non-logged in server is on
        CF set on error
            AX = error code