Why is my computer fan so loud?

"It sounds like the bearings on your fan have worn. The cheapest solution is to buy a new fan.

Remove the old one and take it down to your nearest computer parts shop and get one the same size and rating and with the same plugs to replace it."

"You might want to try the following in order of increasing cost

Get some heak sink paste and removing the fan, cleaning any old paste off and applying a thin layer of new paste, put everything back together ($1-2)
Replace the fan on the heatsink, the fan bearings will get old and noisy over time ($10)
If you're ok to spend $30-40 then I'd just replace the heatsink/fan with a large 1200RPM one."

"It could be that the ball bearings on the fan are starting to stick a little, causing the noise. This also causes the fan starts to vibrate a little and not run as fast, which could be related to the heat.

Replacing fans on heatsinks are usually pretty cheap. I'd looking into picking one up and trying that."

"You mention that you have removed all the dust you can find... There may be dust you haven't found. If dust gets into the bearings or motor it can interfere with the rotation of the fan. This can result in excess noise and will probably lead to the motor giving out.

You probably want to consider replacing the fan entirely.

Is it only the CPU fan that is making noise? I have found that PSU and case fans can also be quite noisy when they are failing."

"You might consider installing more case fans - it could be that the CPU fan is fine, but there's little actual air going into and out of the case, so the CPU fan has to cool to a higher in-case temperature, rather than a cooler room temperature.

Make sure the PSU fan is running well, and look into getting a few 12V case fans that you can run at 5V. Make sure that you have as many fans blowing into the case as out of it, generally intake from the bottom front of the case and blowing the hot air out the top back of the case.

-Adam"