Computer turns itself off

My computer turns itself off, sometimes after a few minutes, sometimes longer, whether it is in safe mode, normal or Bios. Have tried cleaning it out, have checked the temperatures and voltages and everything is within normal range. The computer must be unplugged each time it turns off before it will restart.

Mainboard: MSI MS-7125 Ver:1 K8N Neo4
Processor: AMD Athlon64 3200+

Any ideas what it might be?
Thanks!

 

Welcome to the forum Nik,can you include the name of your video card and post the information from the side of your power supply and memory in your next post Has this computer worked fine in the past and can you think of any changes you have made recently?

Does the computer completely power down instantly? What your describing sounds like a power supply or motherboard issue,double check all your fans are spinning,first try a different power cable and power outlet 'move the computer',if your using a UPS or surge protector remove for the test and if your not using a surge protector get one.

Next remove all uneeded hardware including add in cards,hard drive,CDrom and use one stick of memory,enter bios with these things removed and wait for a crash,if it crashes load fail safe defaults in bios then restart and wait for another crash,then turn on the computer with the power button and unplug it from the motherboard just to double check it isn't faulty,is your computer clock keeping time?

Let me know how you get on.

 

video card: asus en6600
power supply: antec 350w
memory: 2x 512 MB PC3200 Dual Ch 200 MHz
Has this computer worked fine in the past? Yes
No changes made recently

Does the computer completely power down instantly? Yes
...sounds like a power supply or motherboard issue, Yes, or memory
all fans are spinning

first try a different power cable: haven't tried yet - I doubt that it is the power cable since the computer will turn off without me being in the room and stays on even if I wiggle the power cable. I have to switch off the rocker switch on the power supply, then wait for the capacitors to drain on the motherboard, then switch the rocker switch back on before pressing the front panel power button otherwise it will not power on.
and power outlet 'move the computer': haven't tried yet - It is plugged in to an APC surge protector, but only powers itself off instantly when in Windows. If I leave it in the hardware monitor in the BIOS, then it will not power itself off.
if your using a UPS or surge protector remove for the test and if your not using a surge protector get one: haven't tried yet - see above.

Next remove all uneeded hardware including add in cards,hard drive,CDrom and use one stick of memory,enter bios with these things removed and wait for a crash: it only crashes in Windows and sometimes right away, sometimes it takes a few minutes. I have now made it fail 3 times in a row while trying to install the video driver. Not sure if that would be the video card or the memory so I'm running memtest-86 to be sure.
if it crashes load fail safe defaults in bios then restart and wait for another crash,then turn on the computer with the power button and unplug it from the motherboard just to double check it isn't faulty,is your computer clock keeping time? Bios is set to defaults, same as before.

Let me know how you get on.

Memtest-86 returned 2 errors on one of the tests so I'm off to buy some RAM.

Cheers.

 

Glad you fixed it even though I was just chopped liver :-D Your power supply is pretty low on the wattage but its an antec so should be OK,I would try a different PSU if you have one lying around,feel how warm your PSU is getting.