According to the latest Halo Bulletin 343i will be pulling the plug on the Halo 2 PC servers on February 15th, 2013, leaving LAN the only way to play the multiplayer.
To switch gears ever so slightly, we’re sad to report that the service end-date for Halo 2 PC Multiplayer will be February 15, 2013. We’ve been monitoring the population for months, and it’s been peaking consistently at approximately 20 players or less. Those that own this game can continue to enjoy Multiplayer over LAN after that date; however our network services will be turned off at that time. We love you, Halo 2 PC, and you will live forever in our hearts.
If you got any MP achievements that need to finish better get it done ASAP.