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Every two hours, my windows pc shuts itself down and then reboots. I installed a new psu and went into the BIOS and restored the default settings, but nothing changed. What could be the problem and how could I fix it?

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Is it properly shutting down, or is your computer abruptly switching off or restarting? If it is the latter, a component might be overheating. – Paul Lammertsma Apr 16 '11 at 17:53
It's abruptly shuts off approximately 1hr and 54mins every time, even after just shutting down. So I don't think it's overheating. – user76888 Apr 16 '11 at 17:57
If you're still using the beta version of Windows 7, it will reboot itself every few hours to force beta users to buy the retail version. It has been doing that since last March, so I doubt it's the issue. – TuxRug Apr 17 '11 at 1:08

Your computer may be restarting because of a critical system error ( also known as the "Blue Screen of Death").

Most installations of Windows have a default setting that causes them to reboot rather than show you the error message associated with the crash.

If you open your start menu and right click on Computer (or maybe it's called "My Computer"?) and go to Properties.

On Vista/Win7 there should be a link labeled Advanced System Settings on the left hand side-- Click that.

Then under the Advanced tab, go down to Startup and Recovery and click on the Settings button.

Uncheck the box labeled something like "Automatically restart on System Crash"

Now your computer will actually give you an error message when it crashes, so you'll be able to figure out what's wrong with a little Googling.

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I don't think it has anything to do with hardware, because your computer reboots. All the experience I've had with mean shutting down computers just stay off. Have you changed anything recently on your system? Drivers, new software?

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It's been a persistent problem for a few months now. I would accommodate to it and restart it before it forces me to shutdown. – user76888 Apr 16 '11 at 18:00
I am also unable to go to sleep mode. The pc crashes after entering. – user76888 Apr 16 '11 at 18:01

Your comment that it shuts down every 1 h and 54 minutes, even if it's been shutdown shortly before suggests that there is something that executes every 2 hours (or so) and is scheduled using the clock. Have a look in the Scheduled Tasks folder. You may have something scheduled to run every 2 hours. If this thing crashes then your computer may restart each time it runs.

To access the schedule tasks

  • Select Start > Control Panel
  • Click Performance and Maintenance
  • Click Scheduled Tasks
  • Look for a task scheduled to run every 1h 54 m (or 2 hours).

Also, do a full virus scan. Perhaps it's a buggy virus trying to do something at 1h54m intervals.

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As Wayne suggests there may be a scheduled task that is related to the problem, though I would not expect such a task to cause an immediate power-off unless it is touching hardware that is unused at other times. Also, a scheduled task would most likely go off at a static time (i.e. 54 minutes past even hours, rather then 1m54s after most recent power-on).

Another possibility is that you have a power issue. If you are connected to the power via a UPS try removing that from the system. Some USPs perform a regular self-test when not on battery power and if there is some fault with the device this may cause it to cut out unexpectedly causing it to stop providing power long enough for the PC to shut off.

It is worth checking if there is anything in the Windows system logs (under XP, right-click "my computer", select manage, and you'll find the logs under "system tools" / "event viewer" - this should be almost identical under 7/2008/Vista/2003/2000 too) immediately preceding the power cut. Even if it doesn't get chance to log what actually causes the cut, something may be logged that gives you a clue particularly if the issue is due to a scheduled task or similar timed operation.

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Has your CPU fan or cooling system changed? Do you Overclock the system? If you have a Intel Ship you may want to use Intel system Monitor and see if it is over heating (you can find a number of free utils for other chips). If it is maybe a new heat sink and fan may do the trick.

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