Noisy fans

[R.I.P.]

The system's fan (s) is whining loudly.

 A loud fan can be the result of a number of minor problems.
The common cause is dirt. A dirty fan, clogged with dust, is highly inefficient and works harder to handle its cooling duties. As the fan struggles to cool the system, it produces the whirring sound. A quick cleaning should do the trick. If the fan is new and you're still hearing a loud whirring, your problem may be "ambient heat." You need to operate your PC in a cool environment. Many PCs get louder as they get hotter, with the fans spinning faster to keep the system cool. Be certain your PC is clean and cool and you'll run trouble-free.

The best and probably easiest method of removing the dust from the fan(s) blades is to purchase a can of dust-off or similar product . Shut down the machine , remove the side cover or the case . Then simply blow out the accumulated dust. A word of caution ......when blowing the dust off the cooling fan (s) stop the blades from turning ..... ( I use a bamboo chopstick ,it works great )
While you have the case open , it's a good idea to blow out any dust that may be present. Replace the case cover or side panel and your all done . This should be done at least once a year, more often if your machine is in a dusty enviroment .