http://blogs.halowaypoint.com/Headlines/post/2013/01/16/The-Halo-Bulletin-11613.aspx
First Halo title to have unobtainable achievements from it's online being shut off
To switch gears ever so slightly, were sad to report that the service end-date for Halo 2 PC Multiplayer will be February 15, 2013. Weve been monitoring the population for months, and its 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.
#singletear
First Halo title to have unobtainable achievements from it's online being shut off