My laptop keeps making a humming sound that sounds like something is rubbing. The sound stops if i tilt the laptop far back, and at some angles it will start/stop if i place pressure on the laptop (such as when i have my hands on it typing).

I replaced the fans a few months ago but the problem seems to be back again. Ive removed the back cover and checked the interior of the laptop but i cant find anything wrong with it, see : http://i.imgur.com/1R8erHR.jpg

Any ideas? The retailer has no clue what is going on.