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Why does a pc restart automatically, ram seems good, hard discs have been swept by AVG and Avast Pro. Power source is OCZ stable and tested.
System is seriously unstable and reboots within a few minutes sometimes. Managed to install new updates but when I go to restart it doesn't load properly and beeps annoyingly. No overclocking of CPU.
On boot it states that computer is in safe mode, and recommends alteration of voltage in CMOS.

Computer was stable for 2 years with no issues. No upgrades of any hardwar only microsoft updates.

What are the recommended steps I need to take to sort this out, and what are the plausable causes considering the abovementioned?

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migrated from Oct 31 '09 at 14:47

This question came from our site for professional and enthusiast programmers.

How can you tell the power supply is stable and tested? Have you tested it in another system? It's usually the most common cause of reboots.

Another cause of reboots is too high temperature. Is your system cooled enough? Are the fans correctly running to evacuate hot air from the CPU and from the case? It could be that the CPU fan/radiator is not correctly attached and thus the CPU is not cooled correctly.

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I suggest running SpeedFan or a similar utility to monitor the temperature of your components (and make sure you fans are running). If that doesn't indicate any particular problems, Brian's suggestion of blowing out the dust is a good idea. If you're still having problems, try running a burn-in test (a bootable CD that goes through and exercises your CPU, GPU, RAM). Hopefully, it will crash again and identify the failing component. If it crashes seemingly randomly, then it's probably a motherboard or power supply issue.

If none of those techniques worked, and it was my system, I would cut my losses and build a new system... so I had something to work with, then in my leisure time replace components in the failing system until it works, then sell the refurbished system.

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It looks like hardware problem to me. Try to swap CPU, RAM & GPU, one by one, for some which you know are working properly, and see if those restarts stop. This way, you can tell which component (if any) is the cause of your problem.

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I saw this behavior on a machine one time. Turns out the heatsink on the CPU was caked in dust. Everything was fine after cleaning with a can of compressed air.

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There might be a huge dust collection in your computer if you haven't cleaned it regularly.

I have had some cases where the fan (were in power supply and cpu) was blocked by dust bunnies. Cleaned it and everything was ok.

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I had previously cleaned all the dust using a mini vac. and was fairly thorough.
I have a large enough CPU fan and it is watercooled too.
I have tested the PSU on another system and it works fine with no problems.
I am going to try another motherboard and see what happens.

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If you're getting CMOS error messages, it's worthwhile to check if the CMOS battery is misbehaving.

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how do you "check if the CMOS battery is misbehaving"? ^^ – Molly7244 Oct 31 '09 at 18:06
One replaces it. If things have improved - I am right. If not - I am wrong. That's Super User for you. – harrymc Oct 31 '09 at 18:59
Seriously, sooner or later there will be more signs that the battery is failing. – harrymc Nov 1 '09 at 7:51

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