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My computer keeps restarting when it is idle for a while but, i am able to trigger a restart when i start up a game or when i use vlc media player. I checked the event viewer and i got a critical error code 41 with no bug checks.

I have run memtest, replaced my PSU, reinstalled windows from a USB, ran a disk-check, removed my GPU and booted the system from the on board card. I reseated my cpu and reapplied thermal paste as well as cleaning my fans and dusting out my PC.

None of this helped so i tried replacing my CMOS battery and resting the bios which did nothing. I then formatted my HDD and tried to reinstall windows but the system keeps restarting mid installation. What i also noticed is if i run prime95 in blend mode my PC restarts instantly, i am also able to watch videos longer in windows media player than VLC before my system crashes.

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Just some questions that come to mind after my answer that might help solve this: how old are your components? what types are they (CPU is intel/amd, GPU is Nvidia/amd, PSU, etc)? Has this always happened or has there been a time when the PC was stable? RAM/HDD setup? Services running in background aside from the normal Windows services? Any other technical specs you might be able to provide could help as sometimes the answers aren't always so cut-and-dry :) – txtechhelp Dec 17 '13 at 0:49
Most of the components are quite old around 3 to 4 years. – Gundam Dec 17 '13 at 1:04
The build contains: Nvidea gts 250 gpu, Intel core 2 quad cpu, Gigabyte power rock psu and about 4 gigs of ram. The pc was fine up until a week ago. The last thing i did on it was a hard reboot followed by switching it of at the psu switch, the next day i booted it up and the first thing it did when it logged into windows was a restart. – Gundam Dec 17 '13 at 1:14
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It sounds like it's time for a CPU swap test. I had an old laptop that did this, rebooted at random, was very finicky, didn't matter what other parts I replaced I still had the same problem; at least until I swapped the CPU out from a friends laptop (same lappy and CPU), and sure enough everything was smooth. If Prime95 (a CPU burn in tester) is rebooting you immediately, the CPU sounds like a good candidate (or updating your BIOS firmware).

edit: if the computer is able to boot into the BIOS, that means the basic tests have past (the POST) which means the CPU, RAM, VGA, et. al. are basically functioning; this does not mean one of them doesn't have an error though. That being said, if you were in the BIOS for some time and the computer froze in the BIOS screen, chances are very likely it's your CPU or motherboard, at which point the only options are the unfortune CPU/mobo swap test (unless you have enough money to buy some specialized equipment for this kind of stuff, at which point though you're better off just upgrading some of the parts yourself).

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I also thought that it might be the cpu. The weird thing is i can run all the other torture test that prime95 has without fail except for the blend one. The other thing is i am afraid of updating the bios with my restarting at random. It has also started restarting when i'm windows explorer or copying files. – Gundam Dec 17 '13 at 0:26
@Gundam: I agree with txtechhelp. If the tests did not reveal a culprit, you will have to test CPU and RAM on a configuration known to work (a PC of a friend for example), or use a known good CPU and known good RAM on your motherboard. Note, that a RAM test with memtest cannot tell you whether the RAM circuits go belly-up due to thermal or charge build-up issues. I also agree with you being reluctant regarding BIOS update in your situation.... – elgonzo Dec 17 '13 at 4:36
As elgonzo said, if you can obtain a similar rig and do some swap testing that might reveal something for you. If the power has never been fully disconnected (power outage/unplugging/flipping switch at PSU) for a while then something like this is happening, it's possible one of the IC's has popped (they're small enough and in every component that even 1 going bad in the right spot can cause this kind of stuff), and a full power cycle could have caused it...just conjecture, but without some specialized equipment/software it's kind of hard to tell :/ – txtechhelp Dec 17 '13 at 4:53
Damn, this sounds like it would be hard to fix. I Replaced my RAM with a new stick, the system ran a bit longer but failed once more. I have been running the pc in the bios for about an hour or two just to see if it restarts when in the bios and it didn't instead it completely froze up. I don't know if this information is useful. – Gundam Dec 17 '13 at 5:04
That the machine freezes in BIOS is a very strong indication that something is fishy in the CPU or on the motherboard. Since the BIOS usually does not utilize or stress RAM that much and considering the new RAM stick you used, i would rule out the RAM being the culprit (only having a chance of slim to none). That leaves you with CPU and motherboard. It's time for a CPU swap game i think... – elgonzo Dec 17 '13 at 5:35

This sounds like the CPU is overheating. I would recommend you check your thermal paste and/or heatsink. If you remove the heatsink, you'll need new thermal paste to put onto it again. You'll also need to clean off the CPU and heat sink before re-applying the paste. When you go to re-apply it, make sure you only put a small amount, about the size of a grain of rice, when you go to put the heat sink back on.

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I have already reseated the CPU, cleaned the fan and reapplied the thermal paste. – Gundam Dec 16 '13 at 23:20
you try a different video card? – MDT Guy Dec 16 '13 at 23:55
It did the same with the on board card so i doubt it has anything to do with the GPU. I also view my temps using speccy and everything seems fine. – Gundam Dec 17 '13 at 0:20

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