My laptop fan has started to make noise. Kind of a whir or buzz sound. First thought was to take compressed air to it from outside the shell and by taking it apart. That didn't work, so I went and bought a new fan. When I removed the old fan, I actually found where the dust was hiding, but proceeded with the replacement anyway. Now, a brand new fan is in there making the same noise as the old one. What would cause this? Thanks!