Hello,Recently my PC started to reboot without an apparent reason.Sometimes it happens as soon as I turn it on, sometimes it goes on for hours or even days without happening.Sometimes it even reboots during boot before loading Windows (W7 Ultimate 64) . I get no BSOD or any error message. I thought it could be caused by excessive heat but the temperatures are within normal range. I replaced the processors thermal paste just in case but it didn't help...I noticed in BIOS slight voltage fluctuations (especially in VCORE voltage) and assumed it could be my PSU but I'm not sure... The fluctuation is very small (from 1,192V to 1,184V and back).This is the worst problem I ever had to deal with regarding my PC...Any help appreciated.Thank you.

Did you recently change anything like download new GPU drivers, add new software, started running a program or programs in the backround that you did not have running before or changed/added anything else that you can think of?

More details please. Motherboard, CPU bios version, any recent changes?

Thank you both for your help. I appreciate it. I didn't install any new software recently. The last time I installed new drivers for my GPU (GTX470) was in January.Do you think this can be a software issue when the problem can happen before any software (Windows) loads?The only hardware changes I did were done after the problem started.I replaced the processor´s thermal compound but I also re-seated my GPU, re-seated the memory modules (2x2Gb G Skill DDR2) and cleaned all the dust inside the case. My motherboard is an Asus P5 DH Deluxe with a Core2Quad Q6600 processor and I´ve not updated the bios in a long time. I think it's still running Revision 26.02.I thought about updating it now (before made no sense because everything was fine) but I'm afraid the PC will reboot during the process and that can cause all sorts of trouble, right?Please feel free to ask whatever you need to help me fix my PC and thank you once again.

Your board may want your gpu in a particular pci-e slot, and may want ram in particular slots. Your manual will tell you. My board has those "restrictions"...Bjorn

Hugo, remove any overclock if you have any. My QX6700 does this too on occassion, if I turn the PSU off for 10-seconds it seems to work ok. I think my issue is PSU related. Try increasing the Vcore a little bit, maybe a capacitor is weak and needs a little more voltage. Do not flash the bios.

Bjorn,I have tried different slot combinations with the ram and the my motherboard only has on PCI slot where my GPU fits.Thank you for your help anyway.Gary,Removing any overclock (it ran at 3.06 Ghz for years instead of the default 2.40 Ghz) was step two after replacing the processors's thermal compound and thinking heat was the issue. Sorry, forgot to mention that.I used the BIOS ("Jumperfree configuration" window) to increase the CPU Vcore voltage to 1.2250V but it still reads 1.184V in the "Hardware Monitor" window. Is this normal?The other values are:3.3V - 3.280V5V - 5.068V12V - 12.144VYeah, I thought it wouln't be wise to flash the bios in such an ustable system. Thank you.

You may have enhanced C-state turned on ( in BIOS) or what ever they call that down throttling of cpu when running idle, has different names in different systems. Disable that, and have a stable voltage running.Could try OCCT stress test and look at the voltage lines, will expose a faulty psu. Regardless of what HW Monitor says. First don't worry about "failure core #so-and-so", it'll do that. If your psu is fine then look at what other values the test provides.Faulty/damaged ram stick? Run memtest on each stick.B

You can turn off automatic restart on error and read any codes. Also see if there are any errors in the event viewer. When it reboots does it get to windows or does it just reboot in post?Can be anything, hardware, board, or software. Could be difficult to figure out unless you can get some error codes.

Bjorn, I'll check my BIOS for the setting you mention then I'll try the stress tests using those programs.Greg, I've checked and I have automatic restart unchecked but still get no error message. I get a black screen followed by a reboot into post followed by a message asking me if I want to boot Windows normally or in safe mode.Since I increased the VCore voltage my PC has ran for about 4 hours without rebooting. It's still early to say but maybe (fingers crossed!) I solved the problem.I'll report back soon.Thank you!

If you are sure that you did not change anything just before this started then look in Event Viewer/Custom Views/Adminitrative Events and go to the date that it happened last time. Tell us what it says. If you do not know for sure the last time it happened then do this the next time it happens.If you have a Critical Level / Kernel-Power / 41 (63) and if it happens again I would try another PSU.See if someone has one laying around that you can use for a week or so, if not you will need to buy one. Make sure that you get one with enough power to handle your system requirements.

Hello,Recently my PC started to reboot without an apparent reason.Sometimes it happens as soon as I turn it on, sometimes it goes on for hours or even days without happening.Sometimes it even reboots during boot before loading Windows (W7 Ultimate 64) . I get no BSOD or any error message. Thank you.

HiThis may not help you but I recently had exactly the same issue. My system is an win XP SP2 on Asrock 880GM-LE mb, AMD Phenom 965 cpu, 4g ram and a Radeon 5770 graphics card. I was having issues in FSX corruption of the images on my 3 monitors after I had upgraded FTX Australia from SP3 to SP4. I then upgraded the CCC drivers to 11.2 and this did not help.Fortunately I always make images of my C drive, where I have the OS only, and restored an earlier version of the OS. I have not had the problem since. I was dreading going through the hw route of trying to work out if it was a PSU, GPU. MB or whatever.Hope you can figure it out

Hello,Guess I spoke too soon... I assumed I had fixed it because it ran without rebooting for four hours after I increased the VCore voltage but no... It still happens.idahosurge,As you can see in the screenshots there are a lot of Critical Level / Kernel-Power / 41 (63) events.Maybe I do need to get a new PSU. I was told I should get something better than my current one (LC Power 700W). I'll see if I can get one to test my system, if not I'll have to buy one.sunbeam,I already tried what you suggest. I keep regular backups of my system and it was one of the things I tried as soon as this started to happen but it didn't help.Thanks anyway for your help.

OCCT should give you reliable readings of your psu performance. Just a simple cpu stress test gives you voltage readouts that should give you an indication. Your psu isn't the worst in a budget line, but if all else fails, settle for a name brand psu that has good reviews and a silver or gold award.B

Hello again,Here I am with my latest findings.The truth is I still don't know what's wrong with my PC. :mad: Bjorn,I ran the OCCT test for one hour but I'm not sure what to make of the results. I'm not sure the results show evidence of a faulty PSU. Can you please help me interpret these results? Thank you in advance.My PC was so unstable today (reboots every minute or so), I decided to replace my GPU (GTX470) for my old GPU (ATI HD3870 X2).It's been running for 30 minutes without a reboot. Thank you for your patience.