I download fallout from steam yesterday and it finished today,when I go into the launcher and click play my launcher closes and the game does not open i'm am using Windows 8

Do you have a dedicated video card? Or one of those Intel HD4000's?

Did you follow any of the instructions in this thread?

http://www.gamesas.com/topic/1465357-installing-fallout-3-with-windows-78-and-xp/