Halo 3, how do you reset your exp?

[shayla]

So, my brother is playing Halo 3 and he can't go up a rank because his exp. is too high, and he wants to know how to change it.
And since I'm blond and don't know anything about Halo 3, I was just wondering if someone could give me step-by-step instructions on how to reset it for him?
If you could, that would be great help.

 

[farklefreak5]

Tell him to start a game in Matchmaking and then quit out. It takes a long time to do but it will be easier rank up afterward. Most people hate when others do this though. It screws over the team that loses a player and he is seen as a booster. But that's a different story.

NOTE: I think the dude above me is talking about Call of Duty...You can't reach rank 55 in Halo...