You do not
want to prevent a shutdown when the machine overheats, unless you explicitly want your hardware to be damaged.
Disabling shutdown on overheating (which by the way is a hardware function that can not be disabled for a good reason) would be to hide the symptoms instead of healing the cause.
Having said that, we can help you to fix the original problem, overheating. But we need more information to do that:
- Which hardware is in that laptop?
- Is power-saving for the CPU working?
- If you have a dediacted videochip, do you have the proprietary drivers installed?
- Have you checked if the cooling system is free from dust?