I recently built a new computer for a relative using similar parts to one I built a few months earlier. However, the system won't power on! The front LED blinks faintly for a fraction of a second and then cuts off whenever I try to turn on the computer. The fans don't start moving. The only activity on the motherboard is a faint, green light.
Here's what I have checked over so far:
Video card - both removed and in case
RAM - used one at a time and both
HDD and SSD connected and not connected. Same for CD/DVD drive
8 pin connector and the larger 20 + 4 pin connector are connected
All case connectors properly connected
Brass studs in place
I can only imagine that it's either the power supply or motherboard that's defective. I don't even know how I am supposed to know if there's anything wrong with the motherboard since I've never ran into this problem before.
It sounds to me that the PSU is bad, try exchanging it if it's new. Also, double check to make sure there are no loose screws flying around. It sounds like you got the backside of the motherboard down, look around on the top side, sometimes one might get jammed between a chip and a plastic connector and are a pain to spot.