Sony Vaio F Series problem

I have a Vaio F series laptop that I bought about 6 months ago. It's in excellent condition but I'm having a major problem with it. I had installed Windows 8 Consumer Preview on it and (yes, I'm a noob) forgot to dual boot it with Win7. After some time I started noticing bugs that caused the laptop to shut down rather than going to sleep when I closed the lid (and the power settings were fine.) Recently, one day I closed the lid and when I opened it again after some time the computer started but the screen won't turn on. I'm pretty sure there's nothing wrong with the screen as I have never let it come to any harm. The keyboard light turns on and after a minute or so the fan starts spinning unusally fast and makes a lot of noise. It goes like this every time I try to turn it on. Any idea what happened? Urgent help needed!