How do you unlock all levels in Halo, Combat Evolved (1st one) on Xbox?

[Joe]

I went back to the game after many years and beat the following levels on heroic and legendary on the original XBOX:

The Pillar of Autumn
Assault on the Control Room
343 Guilty Spark
The Library
The Two Betrayals
Keyes
The Maw

I still have 3 levels to unlock. How do I unlock them?? Do I need to beat the game on all levels of difficulty before this happens? Is there a cheat to unlock them for XBOX?

 

[SSgt Little]

Try www.gamesradar.com they're good.

 

[Brian]

Yea, u probably beat those on a different difficulty, then started a new game or something.