CPU/Mobo What do I with a CPU that is running hot?

Xarzu

Recruit
I downloaded the tool Speccy and it says my CPU tempurature is over 90 degrees C.
I powered off the computer for the night but in the morning it is still running hot.
What causes this and how to do prevent it?
 

enthusiast29

Skilled
Old dried out thermal paste, dust, clogged fans, bad CPU cooler mount etc.