I recently started building a PC and im using some of my older parts from my last computer to save some money from buying new ones. I have came across this problem and have been puzzled by it for a couple months and your my last hope. When I power on my pc, it turns on for 3 to 4 seconds then restarts to stay on for good. I have no video, my cpu fan runs. at first i thought it must be the graphics card, so i purchased a new one and I had the same problem. I realized that my power supply had been 180 watts and only 20 pins so i bought another( this time 400 watts, 24 pin) hoping to fix the problem. The same problems has been occurring.
my specs if it helps:
intel dp43tf classic series motherboard
intel 2.4 ghz dual core
ati raedon 4350 xfx graphics card
60 gb hard drive (from my old pc, never had a chance to reformat)
2 gb ddr2 800 mhz ram
motherboard led does come on. I have power to my drives and hard drives.