Hi, Basic Evil
I don't know what it is about Fallout 3 on the PC but to my knowledge it seems every one has problems with the game crashing if not most. I know I have had the same problem but I can play the game for a certain amount of time before it crashes.
But what you can try to do is make sure that your Drivers are up to date and the ones you can look for specifically are:
But are you able to post your computer specs?
Because that would come in handy if you could