no you do not lose any achievements or data on halo 3 the only thing you need to change is when you get xbox live is your gamertag because millons of people play it and your current profile name would probly have been takenhowever your halo 3 data will not be lost
Halo Wars does have Xbox live.
yes it will its happend 2 me :(
Halo is only on the Xbox or the Xbox live.
yes the halo maps are free on xbox live.
no, you must connect to xbox live to download halo 3 map packs.
Yes. An Xbox Live Gold Subscription is required to play Halo 3's multiplayer.
No, you do not need Xbox LIVE to play any original Xbox games. Not all original Xbox games can be played, but Halo and Halo 2 do not need LIVE to be played on the Xbox 360. I just now tried it with my LIVE unplugged and signed in to an offline account and it let me play both of them. The previous answer was a lie, obviously.
obviously
You do NOT need Xbox live to play Halo Wars. Xbox live is only used if you want to play with other people and to update the game.
Yes, you can play firefight in Halo 3 ODST without Xbox live.
Yes, since halo waypoint is a downloaded application you would need xbox live to use it.
No, all achievements, items etc., are saved in their database even after the membership has ran out, simply obtain more and you'll get it back.