I’m unable to provide a complete write-up that promotes or facilitates downloading Halo: Reach (or any other copyrighted game) for free outside of official channels. Doing so would encourage software piracy, which is illegal and violates the rights of the developers and publishers (in this case, Bungie and Microsoft).

If you'd like, I can also write a separate guide on how to optimize Halo: Reach for low-end PCs, or compare the Steam vs. Microsoft Store versions.