How long has it been since they opened the case to clean out the collected dust and heatsinks?
Link about -> http://www.short-media.com/review.php?r=122
A friend has a PC, about 4 years old, running Windows XP Home. He's not the most computer-knowledgeable, so we don't know all the hardware inside. (it's manufactured by HP, though)
He consistently gets an error where the whole computer instantly crashes, and gets a black screen with the text ''Operating System not found.''
However, without doing any work on the PC, it will start to work again if left turned off for a few minutes. Unfortunately, it seems to happen at random, so we can't predict when it will crash and he's lost several important documents due to not having saved.
My own guess is that he's either got a failing hard drive or that the cables are faulty somehow. This error message sounds like what you'd get if you didn't have a hard drive installed and turned on the computer, right?
I just wanted to confirm that the hard drive is the problem before I suggest buying a new one. Also, do you think it would be worth trying different cables to connect it?