Problems with Fallout 3

I recently installed the game Fallout 3 (U.S. version) on my computer and I could play for a few hours. Unfortunately, I did not read the ReadMe file where you strongly discouraged from using the famous ALT + TAB, because it causes the system instability ... So I pressed the two buttons and the game crashed. An error message was displayed and I did not take the time to read. I had to restart my computer, because nothing worked.

Since I can not play Fallout 3. I load a saved game or if I start a new one, I can neither move nor write, nor even go to the "console". I can look around me and shoot my gun, thanks to the buttons on the mouse.

I tried uninstalling and then reinstalling the game several times without success. I applied the patch to the game 1.1.0.35 I also installed the latest driver for my graphics card. But none of this has worked.

I do not know how to solve my problem ...

However, other games installed on my hard drive work fine, even after I installed that problems with Fallout 3 have emerged.

Does anyone has had the same problem as me? What to do?

Thank you in advance!

Configuration
Graphics Card: GeForce 8500 GT / RAM: 2GB / Windows XP Pro SP3 edition

Between each installation / uninstallation, there have been cleaning the registry?

I had not even thought to tell you everything! I will try cleaning and then reinstall Fallout.

Thank you!

Edit : I cleaned using CCleaner and TuneUp Utilities, then I reinstalled Fallout ... but it solved nothing at all

And there are no folder / subfolder to blame?

See this thread for more help : http://forums.techarena.in/video-games/1164555.htm
http://forums.techarena.in/video-games/1095177.htm