If you want to have a few more hours of Halo 2 on your Xbox then now is the time. All Live service for the original Xbox will disappear on April 15th and this also affects original Xbox games played on your newer Xbox 360. Same goes for an Xbox Original title that you downloaded through your 360; on the 15th of April there will be no LIVE service.
The advantage of cutting off these old games is allowing Xbox LIVE to expand, and as Microsoft put it “in the next few weeks” more functionality and flexibility will be available on LIVE. [Via Gamerscoreblog]