There is no person who doesnt remmember the good ol' game, Duke Nukem 3D.
Someone develouped a version for it (port) so it can work perfectly on
windows xp. and another software to play with it online
and there are Games Rooms and stuff.
now you might thing that the game is old and doesnt worth playing.
but 80% of the people who started playing it now online, like it alot
and really amazed by the Pro and fun gameplay which surpesses
the gameplay of many new games!
give it a try, you wont regret it.
Check it all out and download everything you need to play here:
www.vachu.com/duke3d at the page: "Multiplayer - How to"