Install
Microsoft .NET Framework Version 2.0
And then
Microsoft Visual C++ 2008 Redistributable Package
Also if you have a codec pack with FFdshow you have to do this.
1. Click Start
2. Click “All Programs” (or just Programs, depending on the version of Windows, whether they’re using “classic,” etc.)
3. Go to the ffdshow folder.
4. Click “Audio decoder configuration.”
5. In the left hand pane, click “Info & debug.” This is the second entry in the list.
6. In the right hand pane, near the bottom, find a check box labelled “Don’t use ffdshow in:”
7. Check that box, and in the text box underneath (it lights up when you check the check box), add “fallout3.exe” (don’t include the quotes). If there is already something in that box, put a semi-colon ( ; ) after what’s already there, and fallout3.exe after that. Do NOT use spaces, since ffdshow will think that’s part of the filename. A valid entry would be “explorer.exe;fallout3.exe” (without quotes).
8. Finally, click “Ok” and start Fallout 3.