in halo 3,how do you replay a level without losing your data or starting over the

[JDOGG1122]

game? becuase when i try it says all progress will be lost.if you can help 10 points!!!
i mean how do i replay a level in the menu without starting over the whole game.

 

[The Great Gate]

when I first bought xbox 360 I used to unplug the main power cord after playing. I realized that when you continue to unplug the power cord eventually you lose all your saved data. Now I just keep it plugged in at all times.
* When you replay a level on Halo 3 you don't lose your data*

 

[S.N.L.Y]

Save your checkpoint