High CPU usage, even after clean install

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valau

Honorable
Aug 13, 2012
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10,510
I have had my computer for a couple years now, running rock stable, but recently noticed high CPU usage along with stuttering in normal day to day task. After running tons of diagnostics and different anti-virus/spyware programs, I couldn't find anything, and so I reinstalled a fresh copy of Windows 7. Surprisingly, the problem persists even after the clean install. I have no idea what's wrong with it... simply opening up a Youtube video or trying to install Word would push the CPU to 100%, and make the machine unusable. I'm starting to think it might be a hardware issue, but have no idea where to start.

Specs are:
-Biostar TH61 ITX
-Intel i5 3570k (running at stock speed)
-8GB DDR3
-ATI Radeon HD 4850
-300w Silverstone PSU

Thanks!
 
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SchizTech

SchizTech

Judicious
Jan 16, 2011
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Which diagnostics did you perform and how did you reinstall the OS (from the Windows install DVD or a restore partition? Did you FORMAT the drive or install over the old copy?). Possibilities to consider are something that is resident in RAM or in your router if you are still infected. You can remove the RAM and re-install with one stick and re-set your router to clear those possibilities.
 
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V

valau

Honorable
Aug 13, 2012
8
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10,510


Ran memtest85, uninstalled tons of programs that created processes that were eating CPU, hoping to find the culprit, ran a cpu stress test, but found nothing. Also used 3 different antivirus programs to look for malware. Are there others I should perform?

When installing Windows again, I deleted the old system partitions, created a new one, formatted it, and then installed in the new partitions. I installed it from a USB stick, since my computer wouldn't boot from the CD for some strange reason. It is a legit copy of Windows though.

Thanks
 
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V

valau

Honorable
Aug 13, 2012
8
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10,510


I used Rising Antivirus (Chinese software), AVG, and Avast!, and am currently scanning the new install with Microsoft Security Essentials. I used my laptop to prepare the USB stick: just created a bootable USB from the ISO file I downloaded from MS. I'll try resetting the router and pulling out the memory as soon as this scan finished.

Thanks!
 
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SchizTech

SchizTech

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Jan 16, 2011
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Well, that won't help if your drive is infected again, I was more or less brainstorming how you could have re-acquired an infection after reinstallation. Was there any other drive or device attached to the PC during the re-installation?

Try scans with Malwarebytes and running Combofix.

 
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V

valau

Honorable
Aug 13, 2012
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10,510


Also, it might help to know that when the computer boots up, everything runs fine for maybe 10 or 15 minutes, and then the CPU usage will spike out of nowhere and make the system extremely slow until I reboot it again.
 
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SchizTech

SchizTech

Judicious
Jan 16, 2011
5,278
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32,640
When it starts to run slow, have you checked to see which processes use all that CPU time in the Task Manager? If so, what is the process name?

On older computers, Windows can slow tremendously due to normal background tasks like downloading updates or running antivirus scans, but with the specs you list those things shouldn't be an issue at all.
 
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V

valau

Honorable
Aug 13, 2012
8
0
10,510


Yeah I have. Doesn't seem to be a pattern... could be any program. For example, Chrome could have two threads using 25% each (on pages like Gmail and Facebook), and Spotify might be at 17%, and something running in the background might be using 20 or 30%. Just seems to be ridiculously high CPU usage across the board, especially for a CPU that I think is quite powerful.
 
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V

valau

Honorable
Aug 13, 2012
8
0
10,510


Haha I'm game to try almost anything at this point. Will do after running the rest of the scans.

Thanks
 
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V

valau

Honorable
Aug 13, 2012
8
0
10,510


So I'm slightly stupid...

While running Combofix, the computer shut itself down, which I thought would be due to either a PSU problem or overheating. I checked my temperatures using RealTemp and they were in the 90s, which is not normal. After opening up the case, sure enough: the CPU fan had stopped working, so the CPU was being passively cooled. I didn't expect this since the heatsink is the newest component in my desktop. Anyways, ordered a replacement part and everything is working perfectly again. The high CPU usage must have been the processor throttling to try to keep the heat down, which would explain why it only happened after 10 or 15 minutes. Sorry for wasting your time, and appreciate all the help!
 
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