The Lost Chapters is the Xbox version plus a heap of added content.
Any actions you choose to take will slowly warp your character's appearance and the way in which other characters react to him it's kind of like Fallout meets Black & White with a dash of Knights Of The Old Republic. If you're unfamiliar with Fable, it's a combat-heavy action RPG with one hell of a hook: you start off as a child, and can live your in-game life - right up to old age - pretty much how you see Ifit. You got it a full year before PC gamers, fellas, and now it's our turn for a treat. Sure, Xbox owners are currently turning as green as the light emanating from their console, but c'est la vie. It's around a third bigger, for starters.
Don't forget, Fable was originally envisaged as a PC title, and it's looking like this might well be the edition that Peter Molyneux and his Lionhead cohorts were planning on making all along. Let's Get this out of the way immediately - Fable: The Lost Chapters isn't going to be a simple port of the Xbox version.