Hi everyone, I hope that you could help me.

The thing is that fallout 3 game of the year edition bought on steam doesn't work. Well it works until a certain moment, I play the game normaly and then after like 10 minutes, the game freeze like I can't do anything. So I shut down the game and I retry but it's still doing this freeze. I have a nvidia gtx 670 and I run on a quad core 2 duo, but before (like 2 years ago) my pc was running the game perfectly... Please help, I can't run fallout 4 so this is the only thing that I have x)

Quad core is the cause of the freeze. See: http://www.gamesas.com/topic/1465357-installing-fallout-3-with-windows-78-and-xp/ It applies to Vista also.

but why before it was working and now not?

I have no idea. I guess you were just lucky.