IP to IP problems with some games

[daunting]

Hi everyone. I have a Win XP system which used to connect IP to IP just fine for games - I as the server or my friend, either way, I could connect to him, him to me. However I foolishly installed Microsoft Wired Home Network software and fought to get things to work - no dice. Uninstalling the software, and reinstalling XP fixed most of the problems for most games. Live and learn - I didn't make a restore point.
Tiger Woods PGA Tour 2003 which used to connect IP to IP just fine, now doesn't, me to my friend, or him to me. The game says it cannot fine a game hosted at the IP addresses.
What I suspect is some port, some setting has been switched by the installation of the Network software, and this setting or port has not been returned to what it used to be.
I have changed a few settings to no avail and scoured the Microsoft Help site. I can't find what to do, never mind a clear explanation of what is wrong.
Any suggestions would be appreciated.