MS is running a new offer in which new purchases of the Xbox 360 in the US will result in a free copy of Halo 3. All you have to do is buy an Xbox 360 by December 21st, connect to LIVE, enter a special promotional code and then you can look forward to receiving your copy of Halo 3 in the mail soon.

If you're more than ready for Halo® 3, but still have an older console, here's the plan for you. Buy your Xbox 360® before December 21, 2007 and we will give you a copy of Halo 3*. Finish the fight in high definition, with new weapons and challenges. Join three friends in Campaign mode, or get an Xbox LIVE® Gold subscription for sixteen-person multiplayer action.

Here's How to Get Your Halo 3 Game

Buy an Xbox 360 console by December 21.
Connect to Xbox LIVE.
Register HERE with promotional code XBX7777, your new console serial number, and a valid mailing address.
And look for your copy of Halo 3 for Xbox 360 in your mailbox!