A defective cooling fan can have disastrous effects on a processor. CPUs need plenty of cooling to exhaust the large amounts of heat produced on the surface from electrical resistance. The cooling fan for your CPU sits directly on top of the CPU in the middle of your motherboard, which lies inside your computer. In an HP D350, you must open your computer's top cover to access the inside and operate on your motherboard.
Disconnect all of the cables connected to your computer and situate it so the rear panel faces you.
Pull the plastic handle on the back of your top cover upward while applying backward force. When the cover frees itself, lift it off. This only applies to your specific HP model. Most computers do not use a plastic handle and use screws instead to hold down the cover.
Press down on the metal clippings on the fan in the middle of your motherboard and push them into the fan to free it. Remove the old fan from the computer and disconnect the four-pin cable connected from the fan to the motherboard.
Take a dry static-free cloth and clean the surface of your exposed CPU of any dust, hair and thermal paste.
Put a drop of thermal paste on your CPU and spread the solution with a piece of plastic until it covers the metal surface with a thin layer.
Mount your new fan on top of the CPU and clip it on. Connect the 4-pin power cable from your fan to the motherboard and close up your computer.