I closed the lid on my 2008 Macbook Pro for about five minutes, and when I came back, it wasn't responding at all after opening the lid. I tried every button on the laptop, nothing worked. I was left with no choice but to forcefully shut it down by holding the power button. When I pressed the power button to turn it back on, the screen was black and nothing happened. I tried resetting the SMC/PRAM, and nothing works. It's just a black screen and I hear the fans running normally, but nothing appears on the screen. What should I do?