From Mexico.purplecow.org
Open up the fallout.ini file in: My Documents\My Games\Fallout3 Find the line:
bUseThreadedAI=0
change it to:
bUseThreadedAI=1
Add another line after it and insert:
iNumHWThreads=2
This will limit the game to 2 cores and prevent the engine bug from causing the game to freeze.
- If the game still crashes write this iNumHWThreads=1