fan or powersupply replacement

Please read this article regarding ball bearings vs. sleeve bearings
Most likely you have a sleeve bearing fan that has failed. If the fan is plug into your motherboard's fan socket, then you should replace the damaged fan with a ball bearing fan. I recommend Panaflo fans because they are very quiet. If the fan is soldered onto the board such as in some powersupplies, then you can either do some solder work yourself or spend some dough on buying a quality powersupply (Antec, Enermax, Thermaltek, Sparkle, Enhance). Buying a quality powersupply is wise choice because you will most likely be able to reuse the same powersupply if you upgrade your computer within the next five years. Another advantage of using a quality powersupply is that it will deliever stable power to your computer which means a stable computer. Most cheap powersupplies have electrical currents that fluctuate wildly. What is worst that some cheap powersupplies don't even deliever enough ampere for the +3.3v and +5V. Inadequate 3.3V ampere will cause computer startup problem. A sign of good power supply is that it has total wattage for the 3.3V + 5V combined and 3.3V + 5V + 12V combined on its label. Most cheap powersupplies doesn't have that because their manufacturers know that they don't stand up to the test.