Hi, I have a 6400 dell inspiron. Its been some time now, and I have noticed that it makes a very low sound whistling sound of some sort. Its not constant, but it like starts then dies down. And when it gets a bit high, it kinda irritates my ears, the sound of it. It isnt loud, but it ,, hmm hard to explain, its like a high frequency whistling (like dogs whistles or something). Any ideas? thanks