For those of you who have trouble hosting ill answer some things that common probelms.
On windows xp when you try to host you must have your xp firewall off to do this go to Start>Control Panel>Network Connection>Right click the current Network connection>Properties>Advance> And make shure the internet connection firewall is not checked otherwise nothing will come in or out when it comes to hosting
Also make shure you have your firewall allow all to allow the game to be hosted.
On windows xp when you try to host you must have your xp firewall off to do this go to Start>Control Panel>Network Connection>Right click the current Network connection>Properties>Advance> And make shure the internet connection firewall is not checked otherwise nothing will come in or out when it comes to hosting
Also make shure you have your firewall allow all to allow the game to be hosted.