I have a dual 2.0 G5 tower (Rev. C) which is over two years old and I have never had any problems with it (knock on wood). The other night something very weird happened. I always put the computer to sleep before I go to bed, and this time was no exception. Yet when I woke up in the morning I heard a very loud sound coming from my office (which is next to my bedroom) and thought that a neighbor was using a leaf blower outside the window. To my astonishment, I opened the door to the office and discovered that the incredibly loud leaf blower-like sound was coming from my Mac. I guess this is how the thing sounds when all fans are revved up full speed, but in the two years of using it for professional graphic design I have never heard it operate at more than whisper quiet. In any case, the machine was completely unresponsive, so I had to hold down the power button for a few seconds to turn it off. Afterwards it started up just fine and has been running smoothly since. Should I be worried? I don't know how long the machine was going full blast, as I was in bed (could have been hours). Could this damage the computer? More importantly, could this be a sign of a serious underlying problem? Very strange that it would wake itself from sleep mode and just "snap"... Any help or advice would be greatly appreciated.