Often the first piece of hardware to cause us grief on a computer is the internal case fan. These fans can give off a really nasty grinding sound after a couple of years, normally due to dust buildup in the inner workings of the fan. Rather then replacing the fan, we can initially try to dislodge the dust.
Dust is less likely to effect the CPU and video card fans because these fans are usually of higher quality and they don’t have the same access to external dust. I would not try this method for these fans as it is likely to do more harm than good.
As a precaution, it is sensible to either remove the fan from the case or to remove the hard drives from the computer. We don’t want any vibrations resulting in this method to cause your hard drive grief. I say this as a disclaimer, but I have never had any problems bypassing this step.
Find yourself a screwdriver, pull the cover off your case and turn on your computer. Hold your PC case steady and strike the sticker on the fan with the butt of the screwdriver. Start with very gentle strikes and work your way up. You should not need to strike very hard to clear out the dust.
I have used this method on numerous occasions and had great success. The worst case is that you break the fan, that you were likely going to replace in any case. If you can be bothered, now would be a good time to vacuum the inside of the machine whilst the cover is off.
It’s primitive, but it works a dream.