I have a HP DC7900 motherboard, im using a Core 2 Quad Q6600 processor, ive bought a heat sink from ebay and put it on, i have 2 gigs of ram and a 450 Watt psu, when i plug it in, it imediately powers up the motherboard, but the processor fan doesnt work and i have no signal coming from the monitor, what could be causing this issue? i know it powers on because after a few minutes the heatsink gets warm from the processor