You're troubleshooting a PC that makes a loud whining sound. When you look at the exhaust fan, you notice a thick layer of dust. What should be done next in this case?

Before replacing any parts, try cleaning the fan. The power supply fan is protected by a grid, and you won't be able to reach it with a computer vacuum or a damp towel. The best approach is to blow it out with compressed air. Insert something nonconductive, such as a plastic knife, between the fan's blades to prevent the fan from spinning and to protect the fan's motor. You will, of course, do this while the computer is turned off.