A computer processor gives off a good deal of heat. When the internal temperature of a computer begins to rise, you run the risk of the processor getting fried, which will destroy your computer. To combat this, computer manufacturers have placed fans inside to keep them cool. Like any mechanical part, however, a fan can malfunction and must be replaced as soon as possible.
Turn off the computer. Remove the power cord and all cables.
Remove the screws which hold the case onto the computer. The case is usually attached by several screws. Pull the case off of the computer gently.
Examine the broken fan to understand how it is attached to the case and plugged into the computer.
Unplug the fan power cable from the computer. Unscrew the old fan from the side of the computer case and keep the screws in a secure location.
Install the new fan into the same location as the broken one. Attach the new fan to the power source once it is secure.