Install Games for Windows and come back and report if it works. I replayed the whole game on Win7 64 bit and the game is still buggy as fuck. I had the radio shipping problem, low fps problem. I stuck through it though cuz it's one hellavu great game.
i have windows 7 professional 64bit on a core i3 @2.13ghz with four gigs of ddr3 with 310m nividia gpu i have installed it about three or four times and i cant get past the vault. i can play call of juarez 2 , prototype, and bioshock
...and if you already have Games For Windows Live installed, uninstall it, download it from here and reinstall it. If you've got an old version of GFWL that can't update itself, it could be stopping Fallout 3 from running, so do all of these things.