Computer seems to shutdown when CPU works hard??

[Husse]

Laptop or desktop?
It seems to likely be heat
You could open the computer and gently try to remove dust from the CPU cooler
Remember always protect against static electricity, preferably a bracelet but one hand constantly on th chassis is ok too

PS
Välkommen till Mint

[meandean]

I would have to agree. It sound like a over-heating issue. Probably just needs a good cleaning.

[rivenought]

I concur that this is most likely heat-related. If you can, unhook all your cables and carry the unit outside. When outside, use a can of compressed air to blow through the power supply, the CPU fan and heat sink, as well as any case fans. Be careful on the interior cleaning due to static discharge as mentioned above.

A clean interior can make a big difference in your machine's performance. I clean my interior every 90 days. Hopefully, it is just regular household dust on your end. If there are any smokers in the house, that takes some extra consideration due to the tar buildup on the components.

Also, something that many overlook is that the thermal compound between the CPU and the heat sink can deteriorate over time. It is possible that a quick re-application of a good-quality thermal compound might help, as well. Chances are that your compound is good, but I thought it might be worth mentioning. Have fun!

[Husse]

thermal compound between the CPU and the heat sink

Agreed - but this can be dangerous to change - the cooler may sit so hard on the CPU that you risk destroying it especially for some Athlons "pre 64"

[rivenought]

Oh yeah, Husse, any time anyone opens a case and starts pulling things out, there is a large chance of breakage (as well as smoke and fire). As for the thermal compound, one trick I have used is waxed dental floss. It is just right for getting between the heat sink and CPU without causing any damage as it releases the bond. Of course, if the compound is holding on tightly, chances are that it is good. If it is flaky/crumbly/dusty, then replacement could be considered.

Now, that being said, kilometerage may certainly vary from person to person. I have used the dental floss method on Socket 5, Socket 7, and AM2 only, and I have always been extremely careful. As Husse says, do not break it if you cannot fix it. I would start with compressed air and blowing out the dust bunnies first of all. Have fun!