HELP!! I cannot save the games and thus cannot re-enter at a save point. What am I missing? Is the disc faulty? Do I need a patch/update? Plz respond

What platform are you playing on? and how far are you getting before encountering issues? i.e. training?

I'm playing only local single & co-op. I did not establish any identity, but used an existing identity from Halo3

So your playing on Xbox360??

You need to create an in game profile in addition to your gamertag profile. When you do this it will ask you to select a storage device i.e. hardrive or memory unit depending on what it indentifies as available. Once you have done this you will be able to play through the training level and the campaign there after which will save at the appropriate points into the created profile.

I hope that helps but if your still unsure or any of the above is unclear just hollar