Why wont my laptop boot up?

Hi, I have a compaq presario cq56 and for some reason it won't boot up. It runs windows 7 (theres the problem) and while I was playing minecraft, and in the midst of playing, a window popped up that asked if I wanted to allow the program to make changes to the computer. Thinking it was a normal windows update, I clicked yes, and immediately the screen went blank and the computer shut off. I was like "da hell Microsoft!" and I tried to turn it back on. It came to a screen that said windows has failed startup. There were also two options. There was "start windows normally" and launch startup repair" I tried to start windows normally bit it brought me back to the same screen. I then let the startup repair run for about an hour but nothing has happened. Does anyone know why it is doing this? P.s. I really need it to work soon because I need it for work and there are important documents on it.