There are times when computers and laptops start heating up and either your whole system shuts down automatically to save its components from being burnt or the overall system performance becomes unbearably slow.
First step towards a proper solution is to install a CPU temperature reporting software. Follow this link to download and install a free software called Speccy from Piriform;
After installation, you can see the general temperatures in the Summary view as below;
For CPU temperature, click the CPU link on the left menu;
Ideal temperature for CPU should be less than 75° C (167° F). When they start hitting 90° C or more, then you need to take all of the following actions;
Replace the thermal paste on your CPU and GPU.
Clean your CPU and GPU fans and their vents by using compressed air or blower to blast out the dust through everything including motherboard, hard disk drive, optical disk, etc.
Replace your heatsink and fan combo, especially when it starts making noise.
For laptops, you can buy an exertnal CPU cooler fan base with preferably two fans. For desktops, install more case fans.