So I just got my Mac Pro a few days ago... and actually didn't get it setup until tonight (long story), but anyways I've noticed something rather odd. If I have my external HDD connected to my Mac Pro it makes a clicking noise when it goes into Sleep Mode or even when I shut it down. It's kind of like "click, click" pause "click, click" and this repeats until I wake it from sleep. The HDD is connected by FireWire 400 and everything is fine when the computer is awake, and when I disconnect the HDD and put the computer to sleep everything is fine. Anyone have any idea what's going on here? The sound seems to be coming from the top portion of the machine.