Should you be the type who loves over-clocking your computer system to maximize its abilities then an upgrade of the factory CPU fan may be in order for you to prevent your CPU from crashing and burning up, literally. The CPU or central processing unit gets quite hot indeed and without proper cooling it can fry the chips and other supporting hardware inside of it.
Aftermarket CPU fans come in all shapes and sizes and vary in effectiveness from ones that bolt onto the CPU with heat tubes and bigger fans to ones that have external intake/exhaust ports to get it cooling faster and effectively. Be sure to check the wiring harness and to keep it out of the way of the fan blades, for it may be expensive but a stuck fan will do you no good!
