Note on archived topics.
02-16-2017 01:27 PM
02-17-2017 04:20 PM
Some things to check while waiting for another answer:
Find the holes where air goes in and out of the case. Blow away any dust accumulating in them. Place the computer where nothing is blocking air going in and out of these holes. Now turn on the computer and check if it now runs quieter. One of my computers produced smoke and stopped working when the side entrance was pushed against a cabinet wall that blocked air from entering.
If it still isn't quiet enough, the noisy fan may be in the power supply instead of near the CPU. To check, remove power for several minutes, then open the case, remove the power supply, open the power supply, and blow out any dust you find. Now put it back together and see if it is quiet enough. This helped another of my computers.
Many computers have a third fan on the graphics card. Blow away any dust in its heat sink also.
Some high-end computers have even more fans, usually not dedicated to anything in particular.
Check if your software shows whether your CPU fan is turning at any reasonable speed. If not, the wire for telling the software how fast the fan is turning may be broken inside, in which case the software will probably tell the fan to turn as fast as it can. In this case, find the parts list for that model of computer and see if it offers any way to order a new CPU fan.