computer shuts down
I have a Hewlett Packard computer that is about a year old. It has Windows XP Home with the service pack installed. The problem is that the last few days when I turn it on, it boots and goes to desktop as usual, but after a while it just shuts down on its own. It could be on five minutes or about an hour before this happens. When it does this it is just like it went into hibernation. The screen goes black and the computer doesn't shut completely off . I can move the mouse and push escape and nothing happens. If I try to go to system restore it says I do not have administrative permission. I am the only one whose name in on the computer. Thanks for any help.