My daughter has a Dell desktop with XP Pro. It has been rather slow for no reason that I could find. Over the weekend it started to switch off for no apparent reason. The were no messages. Now it won't even boot into Windows. When it gets as far as the message windows didn't start properly . . . and I select Safe Mode or Last Know Good Configuration the computer starts to load drivers, a screen-full, then there is a click and it switches off. With the side of the case removed I can see a green light so the power is being supplied.
All the fans work. There is a problem with the keyboard socket which is a PS2 type with an adapter for USB being loose and a message comes up "keyboard error or missing keyboard" I have changed the keyboard around with the same message so plugged the keyboard into one of the rear USB ports. The computer then accepts keyboard entry. When I removed the cover over the CPU that channels fresh air in to cool the CPU I found that one of the clips that secure the CPU unit to the board had broken but the CPU unit seems very secure.
Since these modern computers can be switched off by the software I tried to boot up using my Norton Ghost CD but encounter the same problem. I don't know whether this rules out a software problem or not.
I have wondered whether there is a problem with the power supply button and think that maybe I can bypass it. But don't know how to do this.
The PC is vintage 2003 and I could just buy another one, but as usual there is useful data on it. Not only on the hard drive but also on an additional hard drive that I fitted even though there is no spare enclosure- I just used a glue gun to secure it the bottom of the case. It has worked like that for over two years, with no problems. The second hard drive has a full backup on it.