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Some time ago, the PC gave the same problem. It wouldn't turn on. When i pressed the button, it turned on but showed nothing. I had replaced the CPU and that seemed to work. I didn't use the PC that much, rarely you know. But now, after some time, it gives the same problem.

It turns on, the front light is on, it makes the normal noise the pc makes when it's turned on , but if I try to shut it down by holding the power button it just doesn't work.

So again, I tried replacing the CPU and it worked again. I kept it all day working, just to be sure, and sometimes I would restart it and it would work again. No problems at all.

So I turned it off at night, and next morning it just would make the same problem. So I tried replacing the PSU. And it worked again.

Now while I had the PC with the new PSU, i tried to insert the old CPU, and again, it would turn on.

The same thing, tried restarting too, and it would work. But this morning the same problem happened.

Edit: I also tried another CPU today and yet no signs of working.

I don't know now what to think.

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up vote 1 down vote accepted

The problem was with the CMOS battery.

I replaced the CMOS battery with a new one and no problems at all.

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If the machine does not turn off when you hold the power button, the first thing that comes to mind is that you have not connected the ATX power cables correctly. These are the thin cables that go from your PSU to the various components that need power. Check that you have connected the cable to the power button correctly (it will be connected to pins on the motherboard).

In general, the way to troubleshoot this kind of error is to remove all possible hardware devices and booting again. So, unplug all USB devices, remove your sound card, graphics card and any other PCI cards you may have. Also remove the RAM. You should still be able to boot into the BIOS with no problem.

If your PC now behaves as it should, switching on and off normally, you can start replacing the removed hardware until you find the one that is causing the problem.

If it is not a case of incorrectly connected cables as I suggested, my money would be on the RAM. Faulty RAM can cause very strange behavior. Have you tried running a memtest?

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thank you but I found the solution. It was the CMOS battery. – cprogcr Sep 18 '12 at 12:39

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