Hi Kwingat,
I assume you didn't change the port PokerTH is running on - so the port should be 7234.
Try a ping on the other computer's ip address on both computers. Maybe there is a firewall on one or both of the computers. You can also try a "telnet <ipaddress_of_create_network_game_computer> 7234" on the "Join network game" computer if you know about telnet. If the port can't be reached, telnet would tell something like "can't connect". Unfortunately, there could be many reasons why the connection fails
Do you use the same versions of PokerTH? Don't know if this matters. What version of PokerTH do you use?
Regards
Bernd