Windows 7: Fallout 3 Problem

I installed and ran Fallout 3 fine last night and this morning i install oblivion. and on fallout i get an error right about when i start to hear the music from the start screen, It Says Fallout 3 has stopped working, windows is looking for a solution. just installed windows 7 and it works fine, only game that doesnt work (lots of steam games) . i will continue to look for help, Jw if someone knows how to fix my case in partiuclar.

P.s I opened the program with the Start menu> Options> windowed on and It worked! wat should i do?