Vista SP2 with a dual core worked fine. After upgrading to a quad core and Windows 7, I was lucky if I could play more than 5 minutes without a freeze.
A fine gentleman named Nicholas Head posted this solution on his blog. Along with several others, I can confirm this fix works! (YRMV) Fallout 3: Video/Display Freezes, sound keeps going
by Nicholas Head
7. February 2009 00:35
Ever since Bethesda came out with the 1.1 patch for Fallout 3, I couldn’t play the game anymore. Once I got into the game and started wandering around, I’d randomly “freeze” up… the video would stop updating, but the sounds/music would still play. Keyboard clicks and mouse clicks did nothing, requiring me to ctrl+alt+del and kill the task manually.
It looked like I was SOL until the next patch, but I found some help online:
The game engine has some issues with processors that have more than 2 cores. You can force the game to only use two of them and it will stop the freezing. I haven't had it freeze once since I did this several days ago.
Open up the fallout.ini file in: My Documents\My Games\Fallout3
Find the line:
change it to:
Add another line after it and insert:
This will limit the game to 2 cores and prevent the engine bug from causing the game to freeze.
Surprisingly, this worked like I charm. I do indeed have a quad core processor, so it sounds like this was the culprit. Why 1.1 broke the game for me.. I have no idea. It sounds like Bethesda needs to do some better testing on multi-core processors.
Hopefully this helps someone else out there!