Applying thermal paste to the processor.

You must apply thermal paste or a thermal pad to the top of the CPU. This will help to transfer heat from the processor to the cooler. Failure to apply a thermally conductive medium to the processor can cause it to fail! Unless you use thermal paste, any slight misalignment of the contact surface of the cooler, or even the presence of tiny specks of dust, will prevent heat from being efficiently transferred away from the processor. Thermal paste also fills the microscopic valleys in the contact surface of the CPU (known as the die). Some cooler manufacturers supply thermal paste with their products. If yours did not, it is available from most good computer or electronics stores and costs around two to three dollars.