Computer Problems

Hello, I have recently started encountering problems with my computer. Here are the specs:

Gigabyte DS3-965P Motherboard
Intel Core 2 Duo e4400 @ 2.66ghz (Used to have it at 3.0ghz before the problems)
Geil Ultra 2x1gb DDR2 800
Seagate Barracuda 320gb 16mb cache Hard Drive
EVA Geforce 8800GTS 640mb
Corsair HX520 PSU

Ever since the past week or two, my computer has been acting very strangely. At random points in time, Windows will start messing up; I can't open any programs, I can't open My computer, and nothing will load. When I press the hard reset button on my case, the computer just shuts off. When I try pressing the power button again, the computer turns on then immediately turns off a split second later. After that the power button does nothing. So I switch the PSU off then switch it back on, and it works again. I emailed Corsair about this and they said that it's the motherboard that tells the PSU to turn off.
There are also other times where I'll be playing a full-screen game, and all of a sudden my whole computer will start studdering, rendering me unable to do anything. Eventually the computer will either get a BSOD or just shut off altogether.
Also, sometimes when I turn my computer on when it's overclocked at a stable state which I know works, it'll just start restarting the computer and defaulting back to normal speeds.
Another problem is that the onboard sound on my motherboard seems to be getting VERY crackly in the sound.

All of this started happening recently. I have owned this computer since December of 2006, so it could be possible that the component are just getting old. So far, my assumption is that the PSU is going bad, or the motherboard is going bad. I can get a free replacement of the PSU under warranty, but not the motherboard. Also, HDD Health reports that my hard drive is at 67% health. However, when I went to Seagate's website to get a replacement, I was forced to use a Seagate diagnostic program. After extensive tests, it reported that my hard drive passes, which means Seagate won't give me a replacement hard drive.

Any suggestions on what the case may be? I would really like to get this fixed, because having an unreliable computer that crashes constantly is pointless.

Thanks. I think what I'll do is use Hiren's BootCD and just start going down the list of testing tools it has.

I'd also try resetting the BIOS to the default and see if the problems persist...

Please let us know what you find,thanks

When the system blue screens, you need to know the error message (stop error)Windows OS is giving

Right click My Computer
Click on properties
Click on 'Advanced Settings'tab
Chose Advance system settings
Choose Start Up and Recovery
Uncheck 'auto restart'.

Now you can read the BS error message and do a search to find a cause and solution.

Hmmm, the computer just shuts off? Well, a bad MB is certainly a possibility. And a short could also cause the system to just shut off. I had that happen once. It was a simple short from a fan controller causing the system to die. You might try running the system with just the CPU, 1 DIMM RAM, and video card and HD. Unplug everything else. Optical drives, fans, floppy, everything else and see what you get.

Well, I ran Memtest for 7 hours straight, and no errors at all when I got home. Unless anyone else can tell me otherwise, I think it's the motherboard. So, does anyone have any suggestions for a new P35 motherboard? Here are four that I came across that look nice.

http://www.newegg.com/Product/Prod [...] 6813128086

Also, I want to make sure my Scythe Infinity will fit on the motherboard without any obstructions, because that would obviously be bad if there was, like that DFI Lanparty DK with those tall heatsinks.