text: what's the best site to diagnose computer noise? there is a metal box inside the computer where the power cord plugs in. the fan there (or something) has developed a loud whine. sometimes it is louder than others. 1) what is it? 2) is it a problem? 3) can that be repaired or replaced? the computer is a hp pavillion and two years old, but very constant usage. sounds like your power supply. based on constant usage you may need a new supply which can be purchsed for around 30 dollars.  how often do you clean the fan area by the power supply can make a difference. dust may have developed there and got into the vent for the power supply.  they are relitively easy to replace.