My iMac is only about two years old. I dont really hear a fan running. Should I be able to hear a fan easily? Now that I think of it, I really don't ever recall hearing any fan run. The reason I ask is, the top of my computer gets very hot and after time the top of my screen starts to have black streaks on the top left side and the top of the browser temporarily gets burned into the screen. These smudges, images, and/or streaks go away when the computer is shutdown or after idle time when the computer is not running (basically when it cools off). I know this is probably a dumb question but I figure I need to ask this. Is there a setting anywhere on my iMac for the fan? Other than that, how can I verify that it is working? Thanks!