A heat dissipation system within a housing of a computer is disclosed. The heat dissipation system includes a heat dissipating fan, a temperature sensor, a rotation speed setting portion, and a performance control portion. The rotation speed setting portion is configured to change a rotation speed of the heat dissipating fan in a stepwise manner based on a threshold temperature and a measurement temperature measured by the temperature sensor. The performance control portion is configured to temporarily reduce the processing capability of a processor within the computer in response to a determination that the measurement temperature has exceeded the threshold temperature during a predetermined period of time.