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After about 10 minutes of running, my computer will hang, exhibiting the following symptoms:

  1. Both monitors act as if there is no image being sent to them (on, but blacked out)
  2. The CAPS Lock key on the keyboard will not respond.
  3. The computer appears to still be running: CPU Fan is whirring.

When I reboot, Windows says "The previous shutdown was unexpected."


I've enabled the 'don't automatically restart' on an error, and asked the computer to make a memory dump whenever it crashes, but it hasn't done either.

The problem is that there's no bugcheck for me to go off of, so there's no way for me to determine what the cause is (I think).

Here are my system specs:

  • Intel Core 2 Duo E6750
  • Gigabyte P35C-DS3R w/ 4.00 GB (DDR2 Ram)
  • Nvidia 8800 GT
  • Windows 7

I've tried running the Windows Memory checker, but the system also freezes when using that after about 10 minutes as well.

How can I diagnose the problem with no bugcheck and no ability to run a memory checker?

enter image description here


Running Memtest86 also causes the computer to crash (looks like it doesn't make it through a full pass - it was only running for about 10 minutes when the PC stopped responding).

share|improve this question
Try using memtest86, it runs outside of the operating system. Alternatively, boot from an Ubuntu live-CD and see if the problem happens there, this will help pinpoint whether it's a hardware or software problem. – Renan Apr 7 '12 at 1:33
@Renan Thanks, I'll give that a try. – George Stocker Apr 7 '12 at 1:34
I really do think you accepted the wrong answer here. – Ben Voigt May 6 '12 at 15:42
@BenVoigt How so? It was a thermal issue. The issue was with the video card's fan not running. The answer solved my problem. Why wouldn't I accept it? (Not to mention it's the most complete answer out of all of them) – George Stocker May 6 '12 at 16:28
@George: Because an earlier answer correctly diagnosed that it was a GPU thermal issue, and explained how to record the temperature to a file so you could view the log after your computer froze. You dismissed his answer based on your belief that a GPU crash wouldn't affect the keyboard, which turned out to be false. – Ben Voigt May 6 '12 at 17:38
up vote 1 down vote accepted

I can think of a few things. First, if the amount of time until lockup is decreasing as you cycle the machine, it could mean that temperature is your problem. If you're overclocking, I'd start by disabling that, and if you haven't cleaned out the case recently it's probably time to flush the dust-bunnies to see if that helps. I'm always amazed at how much dust builds up in the heat-dissipation fins on my CPU's heat sink.

As to memtest, you should definitely run that from DOS or some other OS. I believe the latest versions of Windows come with a DOS-based memtest utility that may be accessed at startup from the CD. If not, it shouldn't be hard to download and make a boot CD. If your computer can't pass memtest from DOS, then you've either got bad memory or a problem with thermal/power. You can try re-seating the sticks and possibly disabling multi-channel memory to see if there's some kind of issue with it flaking out. The fact that your system runs for a particular length of time doesn't sound like memory, though.

As others have suggested, it could conceivably be some weird power/sleep thing, so you might try disabling the power management stuff altogether in the BIOS to make sure that's not the case. I've had plenty of systems that won't sleep properly or won't return from it, so I usually disable all that eco-weenie garbage right off the bat. I'd love to save power, but it never works right on PCs.

Finally the fact that you can't get a core dump after configuring it to produce one suggests that the failure is not OS related but hardware related. I'd be really surprised if it turned out to be anything other than thermal/power.

share|improve this answer
I ran Memtest86 from the CD at bootup. Originally I had used the utility that Windows 7 provides from the OS, but after that I tried the standalone version. Same result both times (crashing). – George Stocker Apr 12 '12 at 17:12
It turned out to be the GPU. The Fan no longer works, causing the GPU to hit 90c and then die. This usually took around 10 minutes to happen, so that's why the time was pretty consistent (though I noticed it'd take less time if the system was already on). This still doesn't explain why the Keyboard wouldn't respond, and I don't have an answer for that. After 4 years, this system has served me well, but it seems like it's time to build another. – George Stocker Apr 13 '12 at 0:27
Glad to hear the problem turned out to be sane, albeit not cheap. Yeah, I think you've earned an upgrade, G :) – Phileosophos Apr 13 '12 at 13:16

You may try to monitor the GPU temperature, using RivaTuner for instance. Configure it to log the temperature to a file, keep the temperature pane open and let the system crash. RivaTuner is also able to track the GPU fan speed.

The other point to check might be the BIOS itself: RAM configuration, system temperature and fans. You might want to enable the warnings in the PC Health Status section (if you actually connected the speaker!).

share|improve this answer
If the GPU Crashed, I would still expect the keyboard to register. Otherwise, it's a good theory. – George Stocker Apr 12 '12 at 16:23
@GeorgeStocker Hey my answer was the one you needed in the end ;) I'm not suprised the system is completely hung on a low-level communication issue. GPU locks up, PCIe locks up, bridge locks up, whatever. – TallFurryMan Apr 13 '12 at 8:23
Good call. Virtually all other hard freeze failures will cause the screen to become frozen with the last image. That the screen blanked is a strong hint of GPU trouble. – Ben Voigt May 6 '12 at 17:40

I have the same issue I have found out that windows 7 will start a periodic check if you have less than 25Gbyte free in the partition.

If you can try to free more than 25G in that partition (HD).

Good luck.

share|improve this answer
This doesn't look like the same issue at all. – Ben Voigt May 6 '12 at 17:41

Usually when I've seen these symptoms (system appears to be "sleeping" randomly), I recommend hitting Winkey+U to pull up the Ease of Access panel, which also enables the Narrator. If you hear Narrator, you know the machine is running and the GPU is likely bad. If you don't, you probably have bad caps on the board.

Less likely is a faulty PSU, and even further down the chain is "other" (NIC, audio, USB).

If you use a LiveCD and have no issues, swap in a spare drive and reinstall. It is possible that the drivers or some OS feature in Win7 is exposing a hardware flaw.

share|improve this answer
The system is indeed locked during these points because the CAPS Lock key doesn't respond (Microsoft's own support site uses this as a troubleshooting step). Since even the CAPS Lock key doesn't respond, trying to pull up an operating system function won't work either. The capacitors are solid state capacitors, and normally when capacitors go bad, the system doesn't just stay on, it crash-crashes. – George Stocker Apr 9 '12 at 17:50
I don't treat capslock as reliable given that I've encountered numerous pieces of software that affect capslock functionality. As far as the bad caps go, I have seen an enormous amount of variety in what bad caps will do - shutting down completely, bluescreens, apparent memory failures, partial-shutdowns (what you're experiencing), etc. – EKW Apr 9 '12 at 19:34

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