I have my neighbor's old computer and when I am shutting down in the normal fashion,[start,shutdown etc.]it starts shutting down and just about the time the "it is now safe to shut down your computer" message comes on the screen, I hear "click" and it shuts off itself without me hitting the button to turn it off. Then when I reboot, the scandisk starts to run with the message that I didn't shut down properly. What do I do to repair this problem? Have Windows 98 OS, 6 gig HD.