I built my first PC last night. I switched it on and it appeared to be fine, but then the power cut out and after a second or two it came back on again ... I've noticed the heatsink fan isn't working. When I switch it on it makes maybe one turn and then stops. The PSU is 430w ... intel dual core 1.86, 2 gig ram, I've been assured all the parts are compatible. Does anyone know what the problem could be?