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  PC randomly restarts and freezes 
 Date Written 
george k Aug 31, 2011, 07:50am EDT Report Abuse
For some strange reason my friends pc restarts and if it doesn't restart it freezes randomly. To mention things that might help she just installed Windows 7 (She had Windows Vista). At first it didn't even start,it went as far as the Windows 7 boot screen then restarted over and over again. I took out the rams blew some air to clear them off then it started,got into windows then i used it for some minutes then restarted again,this time it load ok and then it restarted again. So i open the cpu cleared the fan,cleared the cpu,i put isolation then closed it again, i disconnected all of the usb's that where on the motherboard,took the HDD off connected it as an external HDD to another computer,scaned it for errors,it showed that no Errors where found,i checked the ram using memtest and it didn't found any errors. So i connected everything again,it started working ok. It worked for 4 hours using various programs,so i connected everything again,started it up and left it to work over night. Next day i found out that it froze 1:30 hours after i left it working. So i once again disconnected everything left only the fan the cpu the ram the hdd and the dvd,but this time it started freezing randomly,it froze while i was inside windows,it froze while loading windows,and it even froze when i was inside the BIOS. So where is the problem?? Is it in the HDD?All though it passed the test would it still be a problem with it??And since it froze in the BIOS could it be that there is a problem in the MOBO?? By the way i change the PSU as well.

Thank you

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micro Aug 31, 2011, 11:30am EDT Report Abuse
>> Re: PC randomly restarts and freezes
Try running the pc with just one stick of ram.

Did you update the mobo drivers via the manufacturers web site? There could be a slight issue if you used the old drivers from the dvd or from Microsoft.

Check for Microsoft updates.

Did you install win 7 sp1? (i don't know if it will take it with the random reboots).

Set bios to optimum defaults.

It can't be hdd if it froze in bios.
I would have suggested psu if you had not mentioned that you replaced it as i had random reboots with a faulty psu before.

keep us updated.

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john albrich Aug 31, 2011, 11:54am EDT Report Abuse
>> Re: PC randomly restarts and freezes
george k said:
...took the HDD off connected it as an external HDD to another computer,scaned it for errors,it showed that no Errors where found,i checked the ram using memtest and it didn't found any errors....

Some things people often don't know:

1) "memtest" does not test ALL the RAM. There is a small section of critical RAM at the beginning of the primary RAM module that is used to load and run memtest. That section (something like 100KB) cannot be tested. So, if something is wrong with that part of the RAM module, it may later show up as an unpredictable problem when running under an OS like Windows or Linux. If you are using a single RAM module, there is nothing you can do to test that section of RAM using memtest. However, if you have 2 modules, you can swap the positions of the RAM modules so that the primary slot RAM that was running memtest is now in the non-primary slot and that section CAN now be tested.

However, you also need to be aware that "memtest" will only test 32bit systems (up to ~4GB). If you have more than 4GB installed you need to use "memtest86+". While memtest is running, watch the progress of the testing and make sure it shows that it tests all the way to total amount of RAM you have installed. For example, if you have 8GB installed (e.g. 2x4GB RAM modules) and memtest shows it only tests up through about 4GB, then the second RAM module is not being tested.

2) "scanning" a disk for errors using a tool like "chkdsk" or similar only checks the "metadata". It does NOT check the content of the files, which may be corrupt or even "missing" and could cause unpredictable problems when they are actually loaded and running. There could also be a virus that must be scanned for using a self-booting CD/DVD. An anti-virus program that runs under Windows may not detect certain malware because the malware "fools" it or even disables the anti-malware program.

So, if you have not tried this, you need to re-install Windows 7 from the very beginning preferably using Microsoft supplied CDs/DVDs and then see what happens. You may even have to try using a different HDD or even use a partition manager tool. Several freeware programs are available, if memory is working right I think freeware PartedMagic (qparted) is one of them that can rewrite base drive information like the MFT (Master File Table).

3) Also, when you are having problems and nothing else works, it is a good idea to clear or "reset" your BIOS CMOS every time you try to boot. Follow the instructions in your user manual as doing this incorrectly on some motherboards can physically damage the motherboard. For example, on one of my motherboards I MUST turn-off the PSU using either using the rear PSU switch or by pulling out the AC plug and wait a minute before performing the "reset" procedure (which involved temporarily shorting two pins on a specific jumper block). Just using the front-panel switch is not enough.

edit to add:
BTW, given that you said it froze one time while in the BIOS Settings (which means the HDD is not yet involved that particular instance), I tend to suspect the RAM subsystem (which includes the RAM modules, the CPU, the memory controller (if separate), etc. This is why it was #1 on the list.

Please also note that if you are trying to run RAM above 1333MHz on certain motherboards it may not work properly without your experimenting with changes to various voltages, clock speeds, and or multipliers. For example, if you are trying to run DDR3-1600 RAM at 1600MHz you may have to change CPU voltage, Northbridge voltage, RAM voltage, specific RAM timing values, etc. In addition, you need to make sure your motherboard actually supports running RAM at higher speeds...and it may not support RAM certain models of RAM modules. See

Alternatively, you can manually set all your BIOS Settings for voltage and timings to default or "automatic" which should make the settings conform to running the RAM at the globally supported speed (e.g. 1333MHz). But, keep in mind that even then, SOME RAM modules either don't provide the right "SPD" information to BIOS or are not supported on a given motherboard and so BIOS may be unable to automatically set things up properly.

william Bell Aug 31, 2011, 05:05pm EDT Report Abuse
>> Re: PC randomly restarts and freezes

My PC in the garage has been resetting, for no good reason, I thought, for some time now.
I thought I had a bug in the soft ware. Checked every thing, but it wouldn't stay running long enough to find any trouble with the software. Temp. in garage is 98+.
I checked the PC Health and found the CPU temp. was pretty high. Almost at boiling point.
So, I brought the computer in the house, to see If the cooler temp. would help. It ran substantially longer before cutting off.
I checked the CPU temp. at cut off and it was high. I let it cool down, turned it on and started watching the temp from a cold start.
It began to creep up at a pretty fast rate, even being in a cool room.
I took the side cover off, removed the fan and low and behold, the cooling fins are about clogged shut.
Too soon old, to late smart.

john albrich Aug 31, 2011, 05:21pm EDT Report Abuse
>> Re: PC randomly restarts and freezes
william Bell said:
...I took the side cover off, removed the fan and low and behold, the cooling fins are about clogged shut. Too soon old, to late smart.

Yeah...sometimes it's the simple things that bite you in the tuckus, and we often put them on the back-burner in the world of high-tech.

Those dust bunnies can be mean and nasty SOBs to computers.

By the way...if your computer doesn't have a built-in (BIOS) temperature alarm...there are freeware programs out there that can monitor your temps and let you define the alarm set-point. For example, I set an alarm in Speedfan at 55C for my CPU, and it also monitors system temps, HDD temps, system voltages, and fan speeds.

In addition to a local alarm (buzzer, audio file, screen pop-up, etc) some of these programs can run a user-specified program (e.g. shutdown) and some can even send you an email (e.g. to your smartphone) when a specific alarm is tripped.



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