Motherboard Startup Problem

Hello everybody.

I got a very strange problem..and I need some help.

The m/b just don't wanna start (not even the the bios rise), I have to make several shutdowns to the system before he boot properly.

More accurately, I start the power button, the system goes on but after 1 sec gets down (With power on mb on, nothing else). The reset doesn't work (I have to keep the power button for 5 sec to shutdown the power [ATX power shutdown] and I have to make this several times before the system boot properly.

So I try to figure out what exactly is the problem...
M/B, PSU, or CPU?

Thanks

Sorry...
M/B Gigabyte GA-7N400 Pro2, CPU AMD Sempron 1800+ (Socket A), Mem 1024 DDR 400, PSU 350 QTec PFC, VGA MSI 6600 GT 128mb, Audio Creative SoundBlaster Audigy, Windows XP SP2 Eng Pro.

I assume that you have been using this PC for a while and this just started. I would be inclined to blame the Qtec power supply. From a quick Google search it appears that it is junk. If you have a PSU to swap it with, I would do that first. Before you buy another junk PSU, let me know the website that you will be buying it from and what your budget is and I wiil try to find a good one for you.

Try to boot with 1 stick of ram then swap it with the other and try again. Next unplug the case front connections from the mobo header (pins). Draw a sketch where they all go so you don't forget. I'm talking about the power switch, reset SW, HDD LED etc. Also remove anything connected to the back panel printers etc. Also remove the mouse and keyboard. Carefully, momentarily short the pins that were connected to the power switch and note results.

If it still doesn't boot, remove all parts from the mobo except 1 Stick of RAM, graphics card, PSU, and of course CPU. Leave the mouse and keyboard unplugged. Try to boot by shorting the mobo pins again. If it doesn't boot it is most likely either the PSU or the mobo. It could also be the CPU or RAM but it is less likely.

Let me know what you find out.

Reseat RAM and all peripheral cards. Also you can try this. Unplug the power cord from the PSU. Then push the power switch on the case to drain all stored electricity. Then plug the powercord back into the PSU and again turn the computer on. Sometimes that works for me when I have a computer that will not start.