I bought this used XP tower from friend in my building year ago. It was her father-in-laws's. He could not shut it down either. I am 63 and know nothing about the Registry. When you go to start-shut down, it reboots itself. I have been shutting it down by holding the power button until light goes off, but read online it damages your machine. I see a box come up when it shuts down this way but it is too quick to make note of it. Something about dll. What should I do? Just leave it on all the time?