It seems that Fallout 3 does not handle being run on a processor with more than 2 cores, which leads to random freezing.

Fix: Edit the fallout.ini file in “C:Users(your name)DocumentsMy GamesFallout 3” (Windows 7 and above)

In the [General] section, locate the bUseThreadedAI=0 line and change it to bUseThreadedAI=1

Below that, add iNumHWThreads=2.

Save the file and restart Fallout 3.

Note that if you’re having issues where Fallout crashes after starting a new game, it’s most likely due to incompatible video hardware, most notably trying to run it with Intel-based graphics.