Phew, I've just finished Halo (I'm from the UK) and I'm shaking from the experience - what a frantic ending!! This game is now my favourite game of all-time, it's just sooo perfect in every way.

One question... I completed it on 'normal' and want to play through again on a harder difficulty. Now, do I create a new profile and use that or do I just select the first mission from my current profile and choose a harder difficulty? Will it make any difference?