The maker needs to correct the issue.
You didn't tell the make and model but it might be a home built unit. The last time I encounter this they had overclocked the unit as well as forgot the heat sink compound. They felt it was optional.
My pc keeps shutting down when I play computer games or I am doing something demanding.
I've noticed my my quad core is running at a high temp, my core 1 averages 80c when just running & when I play a game or something it can raise to 125c
Card name: NVIDIA GeForce 8800 GTX
Processor: Intel(R) Core(TM)2 Quad CPU @ 2.40GHz (4 CPUs)
Motherboard: Asus Striker Extreme
Memory: 3326MB RAM
Page File: 652MB used, 4557MB available
I have a Tagen 1100watt power supply & I have 2 fans, 1 at the back and a thermaltake fan "cooling" the CPU.
I noticed the fan is only running at 60%