A few months ago I was given a PC by a friend. It was missing a graphics card, so I waited and got one before using it, as I want to use it for playing video games. After finally receiving and putting a new graphics card in, I turned it on, and I got nothing. When switching the power switch on a green light turns on inside the PC, but nothing shows up on the screen, and the fans won't start spinning. I'm VERY new to the world of computers, and would really appreciate some help!