Making sure you have a clean computer is a very important but an often missed step. Because your computer has fans running internally to move the warm air out it pulls dust in with the airflow. Much of this dust tends to gather around the heatsink (metal fins that draw heat away from your processor), or in the ports around the power supply. Never use a vacuum cleaner in or around your tower. To clean the dust out of your tower, use a can of compressed air. A vacuum cleaner creates static electricity which does not work well near a computer.