On the other hand, I did have freezes when I run Fallout 3 in Windows 7 x64. I did the "iNumHWThreads=2" and it didn't worked for me. But I fixed the freezes by using this "Large Address Aware Enabler for FO3"
. Since then I didn't have freezes, 'till I tried "alt-tabbing" in order to go to the desktop (e.g. to read walk-throughs for the game, yeah, I know...) and often, I couldn't return back to the game by "alt tabbing" again.