I had a similar issue to you and network/lan gaming did not work properly for some reason. It works sometimes but not others with no logical reason as to why. I had to use XP to play baulders gate in the end. The GF was keen to play with me and kept moaning, so i did not get time to fiddle too much.
It probably can be got working in vista but i had neither the desire or patience at the time.
There was a thread running around here with all the problems of baulders gate on vista. Both myself and others too had problems with it.
Edit here: http://www.blitzmax.com/Community/posts.php?topic=73227
I even tried it with a straight PC-2-PC crossover cable with a straight 1.1.1.x IP setup - and still no joy.
It probably can be got working in vista but i had neither the desire or patience at the time.
There was a thread running around here with all the problems of baulders gate on vista. Both myself and others too had problems with it.
Edit here: http://www.blitzmax.com/Community/posts.php?topic=73227
I even tried it with a straight PC-2-PC crossover cable with a straight 1.1.1.x IP setup - and still no joy.