Xbox Live Gold members can now download Halo 3 for free until October 31st (when the promotion ends). You can manually download the game through Xbox’s marketplace website over here. The download size is around 5.72 gigabytes in size. If you have a Gold membership, we recommend that you take advantage of the promotion if you don’t have the game already. Hopefully Microsoft can continue offering good promotions like this to boost the overall appeal of Gold memberships.