Okay so I have an Asus G2-S and it's been doing this for a couple of weeks.
I can hear a very high pitched sound coming from the laptop. It sounds like it's coming from near the HDD.
Whenever I do something that is using CPU power it stops making the noise. For example, scrolling the screen in the web browser back and forth and running Super Pi will cause the noise to stop, ONLY until I stop scrolling or Super Pi is finished.
Anyone got any clues?