Random Computer Shutdown

Hey hey
I'm having a problem at the moment which involves my computer randomly shutting down.
The CPU doesn't shutdown completely but the monitor goes from a green light to yellow as if it doesn't recognise that the CPU is on. I try and reset the computer or turn it off and then on again and it is unresponsive.
It often occurs while I'm playing games so I thought it may be the video card(geforce 5200 - 3years old?).
Essentially, I have been able to fix it by unplugging my powerboard that goes to the computer from the wall and leaving it for 10minutes then plugging it in again.
However, the other day it happened to a more serious extent and made the sound of the power going out (zeeeeewwwwwwww). The LCD lights stay on though. My previous hotfix of unplugging the powerboard and then plugging it in again didn't work.
I switched my video card with another video card (geforce 5200x) from another computer and the 5200x worked in my computer and it turned on. The other computer also turned on with my 'broken' 5200.

Since using the 5200x the computer has shutdown once or twice and the unplugging and replugging of the powerboard has worked but taken 30minutes instead.
Any suggestions would be excellent. Motherboard? Power supply? Vid Card? Reformat? not too sure myself
My system is about 4-5 years old.
AMD - 2500xp, 512mb Ram, 80gig hard drive
Thanks alot

 

Try a different power supply if you can (you can pick them up cheap if you don't have a spare one, just to test).

Failing that, my money would be on the motherboard.

 

sorry but i have to say it "zzeeeeeewwwwww" lol that was great

 

Pretty accurate description though? I liked the terminology!

 

replaced my power supply with a new power supply
problem still happens but less frequently
narrowing this down to the motherboard but is there realistically anything else it could be?
any help is appreciated. thanks!

 

Maybe there is too much of a load on the current power supply? What is the sum of the hardware in the system and what wattage power supply are you using. There is an online configurator that will calculate the power supply you need based on your hardware. I can't remember where it is though - I am sure a search will find it or someone will chime in.

 

The cpu is reaching its thermal shut down temp, pull heatsink off the cpu and clean, apply new thermal grease and reinstall. ed

 

tunered. you are a champion
i took the fan off my heatsink and found an almighty cake of dust.
it looked like something out of the discovery channel when they go in the amazon and find giant termites nests that have been undisturbed for the past 2,000 years
thanks for the help. hasn't shutdown since i've cleaned it