solved : Microsoft .net framework "Turn Windows Features on or off", can't start the game on Windows 7

[EvathCebor]

I have Windows 7. I tried to install Fallout 3 but it didn't work, I had a message error while the game was installing Microsoft .net Framework 3.0 saying "Turn Windows Features on or off". The solution was to go in the game's folder (usually C:/Program Files/Steam/Steamapps/Common/Fallout 3). Find the DotNetFX folder and right click on the 64 bits application (if you have a 64 bits system, otherwise right click on the other file) and change the compatibility mode for a Windows XP compatibility. Now apply and double click on the folder. Worked for me. Enjoy your game :-)

[EvathCebor]

If you encountered and resolved this issue, it is also possible you're needing to install the Game for Windows Live application. It is needed to start the game. You will find the setup in the game's folder (GFWLive) as you will find any other stuff the install process may have failed to do.

If the game still doesn't work, you can try this solution :
https://steamcommunity.com/app/22370/discussions/0/527273452881576393/