Computer randomly rebooting itself

Factual Questions
#1

My daughter’s computer (a Gateway, Windows XP machine with an AMD CPU - sorry I don’t have other details available right now) has a nasty habit of rebooting itself at random intervals. This does not seem to have any relationship to what programs are running. It can just be sitting there at the Windows desktop doing nothing, or it can be in the middle of doing something; suddenly it will shut down and restart itself, and soon will be back at the Windows desktop with any programs you might have been running closed down and any unsaved data lost.

I am fairly sure that this is some sort of hardware issue, but I am not very knowledgeable about hardware, and I cannot figure out what. There was some malware on it a while ago, but I restored the operating system (it has a system restore partition on the hard drive) wiping all user installed software, which seemed to cure the malware, but did not fix the rebooting problem. Indeed, it only seemed to get worse (more frequent) with time. My initial, uneducated guess was that the problem might be due to a faulty power supply, but that has been replaced and it does not seem to have helped.

A few months ago, my wife got a friend of hers, Gary, who, apparently knows a lot about computers (I am not sure if he is an actual professional), to take it away and work on it. According to her (I am relying on her second-hand reports here), he had the thing disassembled, and ran lengthy tests on the motherboard, power supply, and other components and could find nothing wrong.

(It occurs to me, however, that if she did not clearly communicate the nature of the problem to him, he might simply have been leaving it running Windows overnight. As it reboots quite nicely to the Windows desktop, it might appear to be fine the next morning even though it might have rebooted several time when no-one was looking. I have not met Gary, and my wife’s account of what passed between them has not been all that clear.)

Gary then reassembled it and (pointlessly, in my view, since I had already restored the OS without avail) wiped the hard drive, and replaced the original operating system (which was XP Media Center) with his own copy of XP Professional. At this point, apparently, the guy fell ill, and we did not get the computer back until several months later. It still randomly reboots.

Can anyone suggest what the problem might be? It has occurred to me that (if the story is being conveyed to me right) if Gary was truly unable to reproduce the problem while he had the machine, maybe the problem might have something to do with the power supply at the house. Although several other computers have been and are currently in use there with out any similar difficulties, could this Gateway be particularly susceptible to mains spikes, or something? Could that cause this sort of problem?

Or…what else might it be?

#2

Have you checked to see if all the fans are working properly?

Every time I’ve heard of this happening it’s been overheating - I had a power supply whose fan had stopped functioning (clearly not the case here, since you’ve replaced the power supply), a friend had a CPU fan go bad, etc.

#3

First thing to do is to disable automatic reboot on system failure, this can be done on either a permanent or ‘per-boot’ basis. This will mean that if an error code is being produced it will stay on the screen rather than rebooting back into Windows.

Press whatever key you need to (usually del or F2) to get into BIOS and see if you can find the PC Health section which will list the temperatures, do this as soon as possible after a reboot to see if it is running too hot.

I would run it through a RAM check as well, download and burn a copy of memtest86 and leave it running overnight, even a single error in a RAM check is enough to bring a computer to it’s knees.

Try running prime95 whilst in Windows to see if this brings the problem on quicker, it will stress the CPU and RAM to 100% and generate a lot of heat.

#4

This was my first thought too.

#5

Agree on the overheating thing. If the CPU fan is not working properly, or at all, or if the heatsink underneath it is unseated from the CPU, or the heatsink vanes are clogged with fluff, the CPU will get hot really quickly and random crashes and reboots are likely.

Another possiblity is a memory problem - you could try reseating the memory modules (take them out, then put them straight back in again - this forces the connectors to make good contact again (they can become poorly connected if over time a film of oxide develops on the contacts)

#6

Yup. Make sure the fans are spinning. If they seem to be, then go into your BIOS (typically DEL or F2 on boot) and work your way through the options till you find a CPU temperature readout. Different machines have different tolerances, but some quick googling should tell you something.

If your fan is spinning and the temperature is too high your heat sink probably isn’t setting on the CPU correctly.

And a guy that “tears it all apart and runs various tests on it” is probably full of crap. The only time something like this is a hard issue to troubleshoot is if it’s a single stick of bad memory, IME.

-Joe

#7

I suffered from the same thing for about two weeks. It was purely random. The computer might run all day or five minutes. I tested the memory, temps, malware and so forth. I reformatted a spare disk. All seemed well until it happened again, proving it was a hardware issue. I went for the power supply. Professionals have a module they can test the power supply with in just a minute. Call ahead to find out if a shop can test it and take it in. I solved my problem for a mere $37.

#8

Memtest86 on a bootable CD will often diagnose that one.

#9

Ditto. This is usually the case.

#10

I forgot to mention that I did a thorough RAM test when this problem first showed up, and did not find anything. (I guess I used Memtest86 - I don’t remember, but I know it involved making a bootable CD.)

Everyone seems to be saying check the CPU fan, but how does one do that? Is it just a matter of taking the case off and looking, or is there an easier/better way? I have never been inside the Gateway, but I know that on my Dell, even with the main case off the CPU fan is still pretty much hidden away inside its own casing. Does mittu’s suggestion of stressing the machine with prime95 amount to a test of the CPU fan?

I take it that if I can confirm that it is an overheating problem, the only thing to do is get the fan replaced.

#11

Another common reason for this is bad capacitors on the motherboard. Look for any leakage or bulging on the capacitor tops.