Instructions
Double-click your "Fallout 3" desktop icon. Select "Options" on the menu that appears.
Increase the game's resolution to match your monitor. Make sure to un-check the "Windowed" option.
Change the "anti-aliasing" and "anisotropic" filtering options to higher values.
Change all of the options under "Detail" to "High" or "Ultra."
Enable all screen effects listed on-screen. Check the box beside "V-Sync."
Click "OK" to save your changes.