F5F Stay Refreshed Hardware Desktop High CPU usage right after reinstalling Windows.

High CPU usage right after reinstalling Windows.

High CPU usage right after reinstalling Windows.

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walee123
Senior Member
737
08-29-2026, 09:01 PM
#1
Hi there! A few days ago I finally decided to put a new OS on my computer (the latest Windows 10 ISO from Microsoft). After the setup was done and I could log into my desktop, I noticed in the task manager that my CPU usage was way over 40% even though no apps or games were running. The biggest processor % was being used by "System Idle Process" and "System Interrupts". I searched the web for answers but nothing worked there either. I already tried to reinstall Windows, installed Linux, unplugged all USB ports, scanned for malware (which was stupid since it was a fresh install), wasted hours in BIOS settings, even ran a RAM test with no errors found. Right now, using the PC is impossible because any demanding game feels laggy and smooth at best due to the system hogging all CPU power. Any help would be really appreciated, thanks for reading and have a nice day!
W
walee123
08-29-2026, 09:01 PM #1

Hi there! A few days ago I finally decided to put a new OS on my computer (the latest Windows 10 ISO from Microsoft). After the setup was done and I could log into my desktop, I noticed in the task manager that my CPU usage was way over 40% even though no apps or games were running. The biggest processor % was being used by "System Idle Process" and "System Interrupts". I searched the web for answers but nothing worked there either. I already tried to reinstall Windows, installed Linux, unplugged all USB ports, scanned for malware (which was stupid since it was a fresh install), wasted hours in BIOS settings, even ran a RAM test with no errors found. Right now, using the PC is impossible because any demanding game feels laggy and smooth at best due to the system hogging all CPU power. Any help would be really appreciated, thanks for reading and have a nice day!

A
aduke253
Member
72
08-30-2026, 08:27 AM
#2
Here are the full specs of your system. Which version of Windows do you have? Please show me screenshots from Task Manager by uploading them to imgur.com and posting a link. The idle process shows how much CPU isn't being used. So if 40% is idle, that means 60% of your CPU is busy working while the other 40% is free for new tasks.
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aduke253
08-30-2026, 08:27 AM #2

Here are the full specs of your system. Which version of Windows do you have? Please show me screenshots from Task Manager by uploading them to imgur.com and posting a link. The idle process shows how much CPU isn't being used. So if 40% is idle, that means 60% of your CPU is busy working while the other 40% is free for new tasks.

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me90526
Junior Member
21
08-30-2026, 03:56 PM
#3
I use computers for years, so I've never had a problem like this one. It's strange stuff sometimes. But the heat is normal because I check it often.
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me90526
08-30-2026, 03:56 PM #3

I use computers for years, so I've never had a problem like this one. It's strange stuff sometimes. But the heat is normal because I check it often.

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CatsGoMeow123
Member
158
08-30-2026, 04:11 PM
#4
You can check the Performance/Cpu section in Task Manager and the Disk/Disk Activity section in Resource Monitor. If you reinstalled Windows, several services might be running right now because they are still working (like defragmenting drives, running Windows updates, updating the search indexer, or checking for Defender). You should also make sure to install all drivers from your motherboard manufacturer's website since you likely missed that step too. Start by installing the Intel chipset drivers first.
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CatsGoMeow123
08-30-2026, 04:11 PM #4

You can check the Performance/Cpu section in Task Manager and the Disk/Disk Activity section in Resource Monitor. If you reinstalled Windows, several services might be running right now because they are still working (like defragmenting drives, running Windows updates, updating the search indexer, or checking for Defender). You should also make sure to install all drivers from your motherboard manufacturer's website since you likely missed that step too. Start by installing the Intel chipset drivers first.

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Dave1304
Member
180
09-15-2026, 12:40 AM
#5
Why are we installing this brand new software or OS? Did you swap out the hard drive that it's already sitting on? Are there any extra things you did besides changing the drive, or are there more drives in your computer?
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Dave1304
09-15-2026, 12:40 AM #5

Why are we installing this brand new software or OS? Did you swap out the hard drive that it's already sitting on? Are there any extra things you did besides changing the drive, or are there more drives in your computer?

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Bmaster5026
Member
229
09-15-2026, 09:04 PM
#6
After I turn on an old computer with Windows, things take forever to settle because Windows Update keeps trying to install new safety fixes. When I put down older versions of Windows 10 on very old machines, the updates pile up and it takes hours just to calm down. A weak sub-2GHz processor and a slow hard drive make this even harder. Take your time. Many years ago, I installed Windows 98SE on an old PC and forgot to cut off the internet connection. Half an hour later, installing McAfee flagged a virus. I know Windows 10 has its own protection called Defender, but it's still possible something else is infected. Did you run MemTest86 on the USB stick while your computer was starting up? Or did you check the RAM with a quick test that only takes minutes? If the problem happens in both Windows and Linux, it might be because the hardware is broken or the BIOS settings are wrong, unless your hard drive itself is dying.
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Bmaster5026
09-15-2026, 09:04 PM #6

After I turn on an old computer with Windows, things take forever to settle because Windows Update keeps trying to install new safety fixes. When I put down older versions of Windows 10 on very old machines, the updates pile up and it takes hours just to calm down. A weak sub-2GHz processor and a slow hard drive make this even harder. Take your time. Many years ago, I installed Windows 98SE on an old PC and forgot to cut off the internet connection. Half an hour later, installing McAfee flagged a virus. I know Windows 10 has its own protection called Defender, but it's still possible something else is infected. Did you run MemTest86 on the USB stick while your computer was starting up? Or did you check the RAM with a quick test that only takes minutes? If the problem happens in both Windows and Linux, it might be because the hardware is broken or the BIOS settings are wrong, unless your hard drive itself is dying.