Instructions
Click "Start" from your PC's desktop and then "Control Panel." Find "Region and Advanced Settings" and click the "Advanced" tab. Change your language to Russian and reboot.
Start your PC again and insert your Fallout 3 disc. Install it, following all of the prompts. Select "English" when asked for an install language.
Click "Start" and "My Computer" and navigate to "C:\Program\Bethesda Softworks\Fallout 3\Data." Find the file named "fallout_default.ini" and open it in a text editor like Notepad or TextEdit. Find the text "STestFile2=" and make sure the text "eng.esp" immediately follows it.
Save the text file and go back to the Region settings. Change your preferred language back to English and restart your computer. Load your copy of Fallout 3. The game's menu text, voices and subtitles should all be in English now.