Hello mariduru,
I expect you are right. Some laptops overheat when running at full capacity. There are a lot of threads urging people to clean dust out of their computers using canned air to blow the dust bunnies off the heat sinks.

Here is the method to throttle down your computer: http://www.worldcommunitygrid.org/forums/wcg/viewthread?thread=2684

The 'Useful Utilities' thread at http://www.worldcommunitygrid.org/forums/wcg/viewthread?thread=2490 has:
1) Motherboard Monitor: http://mbm.livewiredev.com/
Monitors CPU temperature. If the manufacturer does not supply a temperature monitoring program for your board, then see if this program works with your computer. If the temperature is too high, then read http://www.worldcommunitygrid.org/forums/wcg/viewthread?thread=2683

4) Speed Fan: http://www.almico.com/speedfan.php
Another temperature monitor like Mother Board Monitor, but also capable of controlling fans in some systems and even checking some hard disk drive temperatures.

5) Throttle Watch: http://www.panopsys.com/Downloads.html
This can monitor some boards and tell you if onboard temperature control is throttling back on speed, which can otherwise lead to puzzling system performance drops. Consider upgrading fans or heatsink or checking for dust buildup and fan failure if it does show that your system is throttling back. Added: This link has already changed once. If it does not work, use Google to find a download site.