I have an issue with my brothers computer. I have upgraded my brothers computer with a new PSU. I connected all the ends and powered it on. Because my brothers computer is an older one, the new PSU came with a 8pin CPU 12v, my brothers MOBO is a 4pin. So I plugged it in closest to the sides. The PSU's fan would spin, the lights in the front would light up, and I see the RAM indicator lights turn on but I never reach the boot screen of BIOS. I double checked the connections nothing is unplugged. I thought I either fried the MOBO or the PSU was a DOA. So I placed the old PSU back in the computer plugged everything accordingly and it booted up with no problems. I went back to the new PSU, did the paper clip trick attaching the green wire to a black wire and checked all the connections with a volt meter to see if the connections are going through. All the connections are supplied appropriately. So I went back to the computer leaving the old PSU inside still attached I placed the new PSU to the side. I only disconnected the 24pin connection, and the 4pin from the MOBO connected to the old PSU. Using the new PSU connections, I ONLY plugged in the 24pin and the right half of the 8pin into the 4pin on the MOBO. I pressed the power button still the same result. No boot up screen at all, just the fans spinning, both PSU and CPU fans, and the RAM indicator lights turned on. Before I hear people saying did you plug in the video card, the video card does NOT need power directly to it because is old, there are no slots for one. So plugging that in is not an option. I don't know what to do about this I have absolutely no idea what is going on. I cannot get the spec as the moment but I can get them as soon as I can. Thank you for your time.