In its first 24 hours on store shelves, Microsoft’s (MSFT ) epic video game, Halo 3, earned a record-breaking $170 million in sales. Halo 3’s sales broke records set not just by other video games but by theatrical releases like Spider-Man 3 and the novel Harry Potter and the Deathly Hallows. Of course, the sales were no accident. Microsoft tied a huge marketing campaign to the game, and if the sales had come in less than $100 million, it would have been very tough for the company to swallow. Why is Halo 3 so important to Microsoft? That requires some explaining.

Last week, we learned Halo 3 had sold five million copies. Using some simple math (ie looking at that figure compared to global 360 sales), we figured the game had a healthy attach rate. Our math was too simple, and was based on inaccurate presumptions. See, of the five million copies sold, 4.1 million were in the US (whose guns+aliens=cashmoney formula, we forgot, does not apply in Europe).

Bungie have released more interesting information on the new Halo 3 maps due out sometime in the “forseeable future”. O.K. Corral and Purple Reign are discussed here, two brand new ones on top of a remade classic map we learnt about last time. Unfortunately we still don’t know for sure which map is being remade, but from the last piece of information we got it should be a popular one.

Check out what Bungie had to say on what you can expect of the new maps,