Chris Priestly, the Community Coordinator for Bioware on Mass Effect 2, revealed this week on the game's official forums that the highly anticipated sequel is too much content for just one disc, and will be shipping on two (with a three disc collector's edition on the way). His informative responses are below,
Yes, there are 2 game discs for both the PC and Xbox 360 versions, both the Collector's and standard editions.
There is a 3rd disc with the Collector's Edition. This is a movie DvD containing making of and other bonus information.
The PC version is a standard install. You install the information from both discs and then play with 1 disc in the drive. No swapping.
You can install the game to your Xbox 360 Hard Drive as long as you have enough memory to do so and have the correct disc in the drive when you play.
Even though there is a disc swap, it occurs at a carefully planned place in the game (that does not interfere with gameplay) and is done once. You do not swap back and forth. 1 swap and then done.
Why 2 discs? Answer: Because you cannot fit this much awesome on one disc. Hope this helps.