I have a dell inspiron 9200 and about a month ago, when I turned my PC on, the fan (not hard drive) started making this huge noise and the whole computer slowed down. After taking the whole thing apart (I was so proud cos I’d never done that before…I did desktops but never my precious one and only laptop!)….and having cleaned the fans completely, the noise still persisted. I tried doing everything from windows too but nothing helped.
I found an online forum like this and it was such a simple stupid solution…….You can make your fan go at a higher speed if u find ur laptop over heating by pressing Fn+z (Keep Fn pressed and then hit z). Do the same to slow it down.
This solution is for a Dell /any machine which has a Fn key. So try it out. If you are lucky like me, it was a error on my part. I play PC games so Fn is right next to control (shoot) and next to Z (lie-down/crouch) for my FPS! So I must have hit that combination in terror when a monster jumped out at me or something.