So I had a laptop that was recently acting as if I thought it was infected. But it wasnt. In the end it was found that it was Windows 7 update service in background.

Laptop is an older Celeron M 1.6Ghz single-core with 2GB RAM.

CPU would peg to 100% at boot and sit at 100%and everything would be slow to respond. Looking in task manager at what is using up the CPU it shows percentages of use that add up to only about 20% used. Select show processes by all users and the task manager window will vanish for about 2 seconds and come back in which you would think it should now show ALL USERS processes. Yet it doesnt show what is eating up the other 80%. Instantly I'm thinking GREAT a Virus or Malware! Those hide themselves! 


Installed AVG and Malwarebytes and ran both with quick scans and nothing detected. Shut it down and rebooted it about 3 times and finally decided to give it a full scan vs quick scan and both came up with no problems however the AV scan TOOK forever to run with a CPU that was bogged down so I left it running overnight into the next day and it was finally complete.

Frustrated with the laptop that I was going to have to perform a reinstall of Windows 7 to it because its messed up somehow, I look and the CPU is no longer at 100% but now 60-80% in use. I go to shut the laptop off and during shutdown it starts to process 34 updates. These 34 updates take about 2.5 hours to complete at shutdown.

I come back to laptop and its off. I turn it on and it boots. Once desktop is up and services loaded the CPU's single core comes to rest at about 18% in use. I start to use laptop and it runs FINE. No more lag. I shut it down and reboot it again and it once again boots fine.

This laptop is not used MUCH and was probably not used for last 2 months. I was thinking initially how in the world could it be infected, but I had to run the scan when it was not acting correctly. The last thing I ever expected was Windows Update Service in background to "Hide Itself" when trying to see processes from all users to try to figure out what was bogging the CPU down.

Figured I'd share this here in case anyone else ends up with a computer ( likely a weak CPU like mine ) pegged at 100% that makes no sense and virus/malware scans come up clean that it might be Windows Update running in background and leaving it running for a long time and then rebooting it might fix it when all of a sudden it completes the updates at shutdown.

Next time I see this behavior I guess I will just be patient and let the computer run for like 24 hrs and then perform a reboot. 

Additionally its telling me to take the Free Windows 10 UPGRADE but when I attempted to do that it then states that this computer cant take the Windows 10 upgrade because the 915M chipset is too old. Yet microsoft doesnt have a routine to make the Windows 10 upgrade disappear from trying to get you to upgrade when the computer clearly cant run it. So I have to tell it to go AWAY with the X (close window) when it pops up telling me how great Windows 10 is and that I should upgrade to it. See Here...Thanks Patio.

I tried the method of uninstalling KB3035583 before and black flagging it as unwanted before and it comes back, so I have ignored the Win 10 annoyance on some other Windows 7 systems. I could just keep uninstalling it I suppose and flagging it as not wanted, but Microsoft is pretty insistent at pushing 10.  I use GWX Control Panel after running updates to get rid of the Windows 10 icon if it reappears.Gonna try the control panel method tonight.