I purchased this game through steam. And I was just wondering why its not keeping track of the acheivements? My new vegas game is having no problem with that. I did buy that one from a store though. I tried to enter the key as activating a game, but the key comes up invalid. and I double checked the key, and its all typed in correctly. so this is a minor issue, but I was just wondering why this is happening?

Why do you keep asking stuff in here that STEAM is where you should ask?

http://www.gamesas.com/topic/1408086-does-the-game-install-after-downloading-from-steam/

Aren't the Fallout 3 Achievements done through GFWL?

Yup, double checked. Achievements for Fallout 3 are tracked through Games For Windows LIVE. There are no Steam achievements for Fallout 3.

That key is for logging into "Microsoft Games for Windows Live" Nothing else.

Hit the "Live" button in the Menu , follow instructions. It will ask for it.

If your haveing problems with GFWL. There's some fixes for that. Just come post back with what its doing.