Newly built PC turns on and off randomly


So I'm having a strange problem. I bought an Antec 200 case for a new PC I put together [shown here] and when I connect the Power and Reset wiring to the motherboard, the computer has a tendancy to turn itself on and shut off a few seconds afterward.

When I first built the computer, and flicked the I/O switch on the power supply on (I), the PC immediately turned on, then shut down a few seconds later. Pressing the power or reset buttons didn't actually seem to do anything, and it would continue turning on and off.

The strange thing is that I disconnected the power and reset wiring and used a screwdriver to short the power pins to turn the computer on. It runs flawlessly when I do it this way, and I'm actually using it right now to type this.

I fiddled with some cables I noticed were connected to the power/reset switches that seem to ground them by connecting them to the case, and the computer ran fine with the power/reset wiring plugged in for a day, but my family told me that they saw the computer turning on and off randomly throughout the day, later on.

I tried googling this issue but most people seem to think it's hardware related, and I don't know enough about grounding and circuits etc to understand what may be happening.

Any advice is appreciated.

Oh, and yes, I double checked that I had the +/- ends of the wires insertted properly...
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  1. Just a guess, but this sounds like what might happen if the power button was constantly depressed -- powers on, then after a few seconds of "holding" the power button, it thinks you're telling it to shut down. So if something is causing that switch to constantly send a signal as if it's depressed, maybe that could do it.

    What happens if you just remove the wire that connects the power button to the motherboard, and connect the reset button wire to those pins instead? If it works that way (i.e. using the reset button as the power button, and having nothing connected to the reset button's pins), it would indicate that the power button or the wire itself is bad.

    I've got a machine that's having similar issues in another thread, and while this is somewhat different, doing this test could at least help rule in or rule out a couple of potential problems. And who knows, you might get lucky and find an easy fix.
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