Well when you first start you pc up you need to hit the DELETE button to enter setup.(It usually tells you when to do it) Then you need to go into your plug and play seetings. Change your VGA snoop setting to disabled. This will make it so your computer does not have permission to turn itself off. There is another thing that will turn your PC off when playing this game. When you snip on the first level at the guy on walkway. My dad had a serious problem with this. He did not snip on that one part and could snipe the rest of the way. I think that this is just something wrong with the DEMO so dont worry. It is really a good game. C YA