I have been having this constant problem with my Acer product lately. While the computer is unplugged, at a random time, it will power off, ending with a sudden click sound, and I'm assuming this is the hard drive powering down. I talked to support about this issue, and they said to hold the battery remove button on the bottom of the unit, but I had no luck. I found High Performance mode to at least suspend this from happening. I do not belive it is an overheat but im not completely sure. I would love to get some help with this problem as for I use the unit for school and I have lost many important documents.