I could be mistaken but I believe you use the product key in the box and activate Windows Live.
Originally Posted by AntiTalent
As I posted above, Fallout3 will launch without a CD if you just launch Fallout3.exe, and not the falloutlauncher.exe
You'll need the CD to use the launcher to change any of the main settings (resolution, AF, AA etc), but if you're happy with it, you can put the cd away no problem.
Might need to register for GFWL first, I don't know about that - did it when I installed.
I think the number of games you can register in steam is actually still quite limited right now, don't think it'll work with FO3
Originally Posted by Puscifer
You can register in-game. After you start the game go to the option that says LIVE and if you don't have an account you can register one through there. Fallout3.exe works fine without the cd for me, I just changed my shortcut to point to that instead of the launcher.