iv seen a few people having issues with playing halo 4 on there consoles and they are all saying the same thing when i load disc 2 it asks to insert disc 2 but you only need disc 1 to play multiplayer, forge, campain, ect. so load disc 1

you only need disc 2 for the files

disc 1 is for playing the campain and multiplayer

hope this helps even knowing its straight forward