I've recently been building a computer and I have everything installed except for the hard drive which hasn't come in the mail yet. The motherboard and fan's are connected to the PSU. When I plug it in, there is a green light on my motherboard to show that it has power, but then when I press the button to but it up the fans barely start to spin and the front panel leds flash just briefly and then it goes back off. Any help at all?? Thanks