in a completely quiet room? If so, what's the sound? What's a "normal" sound? (I have a 250 GB, 5400, Model ST9250315ASG) In a quiet room, I hear it whirring, but I'm not sure I could call it a buzz...more like a light whine? Is this normal? Just the heads spinning? I can't image any spinning hard drive can be truly silent in a totally quiet environment... Is this right?