At random times during the day, there's a loud noise coming from my PC. It sorta sounds like a clicking noise, get's louder and softer, but it has been loud for over an hour now.
Most computers have at least 2 fans, sometimes up to 4 fans. Over time, dust will accumulate throughout the insides of your PC. When dust clogs the fins of the CPU heat sink, it reduces the airflow required to keep the processor cool, as it naturally runs hot. When the CPU get's too hot, it signals the fans to run faster, to draw more airflow, to cool it down. But, since the dust has clogged up everything, air cannot pass and cool the CPU. The fans will then run at maximum speed, and that is the loud noise you hear. Also, the PC may suddenly shut itself down to protect itself from over-heating.
If the fans are a bit worn out, the blades may briefly contact the sides of it's housing and make an even louder noise, which is sometimes confused with a hard drive going bad.
The fix is to grab a can of compressed air and blow-out the entire inside of your PC. Make sure to clear the vent holes around the outside of the PC case. In severe cases, you may have to remove the fan that sits on top of the CPU heat sink, in order to clear out the dust buildup on top of the heat sink.
