I have had my new Mac Pro for one month. It sits on an old parquet floor. I placed it in an area where it doesn't shift or move easily and seems quite steady and stable. Tonight I heard what was like a rather loud vibration noise, almost as if a piece was loose. When I lifted the machine off the floor a bit from the front, the noise disappeared eventually. A friend suggested that it might be dust or a loose fan, but it's only been used a few weeks, and when I added an additional HD a week ago, the innards didn't look very dusty. I saw some dust but very little. It's happened twice, and both times after lifting it and setting it down and slightly moving it on the floor, the noise disappeared. Any ideas on what is causing it? It almost felt as if when I lifted it that the metal on the frame itself was making the noise, but who knows. thanks for any input on this.