from another board...
Play your XBox multiplayer games online without XLive:
XLink Kai is a global gaming network - bringing together XBox, Playstation 2, Gamecube, DS, and PSP users, in one integrated community. It is software running on your PC or Macintosh that allows you to play system-link enabled games online for free. Kai is the only service that is not console specific, and boasts one of the friendliest communities available.
YES, HALO2 can be played on this network. Grab this software here:
http://www.teamxlink.co.uk
To find people and play in a team or ladder for XLink Kai go to here:
http://www.weplayhere.net