A user's desktop computer slows down after a few minutes of use, and the fans...

A CPU fan is a component that cools down the CPU, which is the main processor of the computer. If the CPU fan is failing, it can cause the computer to slow down and the fans to alternate between silent and very loud12. This is because the CPU fan cannot maintain a consistent speed and airflow to keep the CPU at a safe temperature. When the CPU gets too hot, it throttles its performance to avoid overheating, which results in a slower computer. The other fans in the computer also try to compensate for the lack of cooling from the CPU fan by spinning faster and louder2.