processor fan runs fast and makes loud noise?

HP Compaq Desktop D530.

To reduce the fan noise, open the PC Case and clean the fan. Also, proper ventilation keeps the system cool and the fan runs at lower speed.

But this did not helped.So took it to pc repair shop and processor needs to be replaced.After replacing processor its working,the problem solved.The pc repair center,told,that due to getting old,the processor was overheating.And this causes fan to run with more speed to cool the heating processor.