computer shuts down with intensive CPU tasks

[bzhu5]

Recently, my computer has been shut off immediately (no logout/shutdown screen, just complete power shutoff) after I make it do CPU intensive tasks like virusscanning or playing a game. I opened my computer, and saw that the northbridge fan was not spinning, so I replaced it with a northbridge heatsink.
Even after that, my computer still has the same problem. The CPU temperature is around 61 or so every time it shuts down, which doesn't seem to be too high.
Also, is this even an overheating issue or a power supply issue?

Thanks

 

[Omnipotent]

If you have it set to shut down @61 or so then it will
check that

 

[Titanion]

If the cpu is 61c everything else might be too hot as well... get fans blowing in and out of there... and get the cpu temp down to 50c at load... take the case cover off... blow dust out of your heatsinks... open a window... ya, it might be something else, but just because your sensor reads 61c does not mean that it is not even hotter than that, and in my opion, 61c is, indeed, too hot...

<font color=red><b>NF7-S/Mobile Barton 2600+
210x12.5 1.8V
1GB XMS PC3200
9500np modded to 9700np</b></font color=red><font color=green><b>
NF7-S/Unlocked Barton 2500+
200x11.5 1.76V
512MB XMS PC2700
Ti4200

 

[holliswhy]

what spec? ie. which motherboard, ram, gfx card and cpu?

I love my pc
but my pc hates me...