Hi I just built a new pc and it only boots up after a couple of tries. I have a core intel i5 3570k CPU a asrock z77 extreme 4 mobo, GTX 670, gskill ripjaws 8gb, a rose will 650 watt psu. Any idea what it could be? The fans and lights come on and it shows the asrock symbol but after that the windows screen does not show! Any help would be greatly appreciated! Thanks in advance