Fallout 3 is not working on your computer either because it is not compatible with your system or it is not installed correctly. The game works only on computers with the following minimum configuration:
- CPU: Intel Pentium 4 or equivalent processor;
- CPU Speed: 2.4 GHz;
- RAM: 1GB System RAM (XP)/ 2GB System RAM (Vista);
- OS: Windows XP/Vista
- Video Card: Direct X 9.0c compliant video card with 256MB RAM (NVIDIA 6800 or better/ATI X850 or better).
If these requirements are fulfilled, remove the game from your computer and then install it again. If you're trying to run it on a Windows 7 or Windows 8 machine, try applying the instructions from the related question.