Computer turning on for a second then turning off

[icomatose]

Hi everyone, so I had this computer for about 4 years now and I never had an issue with it except the graphic card that I changed a year ago.
However, recently it would turn on for a second or less then turn off, I checked inside my case to see if there was any loosen screws (on both sides) but everything seemed to be in place. I then unplugged all the wires then plugged them back in and then my computer started to work again. Next time I turned it off, same scenario. Turns on for a sec then turns off... Thinking it was my power supply, I tested another power supply from a working computer and it worked fine till again I turned my computer off. So I was wondering what could be the problem.
I would really appreciate your help, thanks

Specs:

Prebuild Acer Aspire AM5620-E5301A
Processor: Intel Core 2 Quad Q6600 / 2.4 GHz
RAM: 4GB DDR2 (added 1gb 2 years ago)
Graphic: ATI Radeon HD 5570 1GB
HDD: 500GB SATA
Power Supply: LITEON PS 6301-08A // Also tried a Mios KY-550 ATX
Motherboard: Acer original motherboard

Running on Windows 7

My guess is that it would be the MOBO (which would suck alot..) however the fact that whenever I unplug everything that has to do with the power supply then plug back in makes it work till I turn it back off is making me wonder.. Also I changed the power supply and same problem is reoccurring.

 

[poodog477]

try unhooking every thing and hook back up 1 by 1 it takes time when it starts the shut down what you hooked back up is the trouble. Don't rule out the memory it will do it too.

 

[icomatose]

I unhooked 2 sticks of ram and it seems to be working fine. I'll have to check if the ram is defective or the 2 slots.
Is there any software I can use to test that out by any chance ?

 

[gwusimm]

I have the same issue. I will try taking out my memory once I get home.
Did you try to plug those 2 memory sticks into the slots where the rest is currently plugged in to test if it's memories or slots?
Let me know.
Thx

 

[icomatose]

Sorry for the late response I've been pretty busy lately.

So my computer boots running on 2gb of ram but not with 3 or 4gb
After testing the ram a bit, I found out that any combination of 1gb sticks (any 2 sticks together) placed in any of the 4 slots will make the computer boot just fine, but if I add a 3rd or 4th stick, it'll turn on for just a sec then shutdown.
I'll sometime be able to boot it up with 4gb if I play around abit (changing the sticks to different slots) but then as soon as I shut it down..same problem occurs.

It looks really odd because it used to run fine and one day it wouldnt boot.