Computer turns off a few seconds after startup.

Alright, so here's the situation:

After coming back from a vacation, I noticed that my computer was off. There wasn't a power surge or an update my computer installed. After trying to power it back on, I noticed it wasn't working. Afterwards, I disconnected the power cord in the back and plugged it back in, flipped the switched, and powered it on. It worked, for a few seconds, and then sparks flew out of the top of the case and I could smell smoke. I quickly turned it off and tried to remedy the situation.

After this incident, I deduced it down to two potential problems: a faulty PSU or a faulty Motherboard. I replaced the PSU with another one I had in a different machine. It was odd, because the only thing that the PSU powered up was itself, and the case fans and motherboard wouldn't power on.

I decided to order a new PSU and Motherboard. I hooked it all up with my other components and crossed my fingers. Somehow, it was doing the same thing: the PSU would power up, but the Motherboard and case fans were off. I came to the conclusion that the one variable held constant was the CPU Fan. It apparently burnt out, so I decided to put in an older CPU Fan (this one is my stock fan and was a bit inefficient at dissipating heat, so I replaced it). All of a sudden, it worked! So I decided, since I no longer needed the new motherboard and PSU, to go ahead and return it, and revert back to my original setup with my old motherboard and PSU. Once again, it powered up just fine.

I was able to get passed the BIOS and get passed the Windows splash screen. After logging in, everything seemed normal: all the hard drives were reading, everything seemed fine. Until a few seconds after the startup, and as soon as it started to load up some programs, it would just turn to a black screen.

Thinking this would be a graphics card problem, I rolled back my driver and see if that solved anything. Unfortunately, it did not. The symptoms I have been having is this:

The screen goes black after a few seconds of startup. At this moment, the CPU reads somewhere between 55-59C, which is generally normal for me. The case fans are STILL ON and the CPU fan is still blowing. I no longer hear the harddrives thinking. The NUMLOCK key on my keyboard is still on, but does not function (as in, if I were to push NUMLOCK, it doesn't turn off). My mouse is off too. Now here's the weird thing: Attempting to hard reset (as in, hold down the power button on the front of my case) doesn't seem to work. The only way to shut down the computer is to flick the switch in the back of the PSU.

At this point, I am literally out of options. It's not the CPU Fan, I just replaced it. It's neither the motherboard or the PSU, since I replaced both and had the same symptoms. It's not the graphics card because I rolled back the drivers.

This computer is driving me insane, and it has been unfixed for the past two weeks. I don't even know where I should start next.

My computer build is as follows:
AMD Phenom II X4 3.4GHz
16 GB Ram
ATI Radeon 5770
Windows 7 64-Bit

If anyone can please lead me to the right direction, that would be fantastic.
2 answers Last reply
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  1. The problem lies in the old PSU, replace it with the new one. Why take risks when you can afford a better PSU. Please post the make of your PSU.
  2. rounakr94 said:
    The problem lies in the old PSU, replace it with the new one. Why take risks when you can afford a better PSU. Please post the make of your PSU.

    I'm not sure if you're reading the entire message, but I swapped out the PSU... twice...

    Current PSU (from my current build):

    Second PSU (from another build):

    Third PSU (purchased from and then returned to Newegg):
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