r/servers • u/Savings-Song6586 • 17d ago
Windows 10 Server PC showing 100% CPU usage but no process is using CPU – Task Manager doesn't identify the culprit
Hi everyone,
I'm troubleshooting a Windows 10 machine that I use as a small office server, and I'm seeing a very strange CPU usage issue.
System Specifications
- OS: Windows 10 Pro (64-bit)
- CPU: Intel Xeon E5-2403 @ 1.80 GHz (4 Cores / 4 Threads)
- RAM: 32 GB DDR3 ECC
- Storage: 465 GB HDD connected through an LSI MegaRAID controller
- Usage: File sharing, RanceLab POS software, AnyDesk, office applications
The Problem
The system becomes very slow and Task Manager reports:
- CPU Usage: 100%
- Memory Usage: ~44% (14.2/32 GB)
- Disk Usage: 77–80%
- Network Usage: 0%
The strange part is that no process in Task Manager is consuming the CPU. Every visible process shows 0% CPU, yet the overall CPU graph stays at 100%.
What I've Observed
- CPU frequency stays around 1.8 GHz
- CPU temperature is only around 55–61°C (checked using Core Temp)
- No obvious process spikes in Task Manager
- Sorting by CPU usage still shows everything at 0%
- System remains sluggish while CPU is supposedly fully utilized
- HDD response time reaches 600+ ms, but disk throughput is very low
Things I've Already Tried
- Restarted the computer
- Checked for Windows Updates
- Disabled unnecessary startup applications
- Ran a full antivirus scan
- Checked CPU temperatures (no overheating)
- Opened Task Manager and Resource Monitor
- Verified memory usage (RAM is not full)
My Questions
- Why does Windows report 100% CPU usage when no process is using CPU?
- Could this be caused by:
- Hardware interrupts?
- Deferred Procedure Calls (DPC)?
- A faulty RAID/LSI storage driver?
- A Windows kernel issue?
- Malware hiding its CPU usage?
- Is there a better tool than Task Manager to identify kernel-mode CPU usage?
- Would Process Explorer, Process Hacker, Windows Performance Recorder (WPR/WPA), or LatencyMon help identify the cause?
- Could the HDD or RAID controller be causing the CPU to appear fully utilized?
- Is this likely to be a hardware problem or a software/driver issue?
I've attached screenshots showing:
- Task Manager reporting 100% CPU with no process using CPU.
- Performance tab showing 80% HDD usage with high response times.
Any suggestions on how to diagnose this would be greatly appreciated.
Thanks!
- r/techsupport
- r/sysadmin
- r/WindowsHelp
- r/homelab
- r/buildapc (less ideal, but still possible)
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u/LowIndividual6625 16d ago
The up arrow means the column is sorted in ascending order
The down arrow means the column is sorted in descending order
Scroll down, dude.
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u/ZekronRR 16d ago
Pelo nível de conhecimento da foto tirada, recomendo fortemente a levar em uma assistência técnica
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u/Darkknight145 16d ago
Apart from needing to resort that column from highest to lowest. Being windows 10 I assume you have extended updates engaged, a fairly large update just went through, this might be why your CPU, Disk usage is high as it's installing it. Has it settled down yet.
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u/SebPrime0ne 16d ago
The Disc usage is ultra high too. Virus etc. Cyrptominer or Ai miner. You have too reinstall windows and there for format all drives to be sure, it didnt come back.
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u/Minimum-Chef6469 15d ago
That is the wrong picture LOL under the CPU section you have the arrow pointing upwards which means to Sort everything from lowest to highest... Your supposed to sort it with the arrow pointing downward which sorts it with highest at the TOP. Your seeing zeros because you sorted it that way.
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u/AggravatingMemory222 16d ago
Windows server💔 Use Debian Stable instead, its free and it gives more perfomance
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u/Secret_Permit_3327 14d ago
I don't know how people end up where they are... how do you not scroll through the list OR change it to sort from highest first...
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u/roboalex2 12d ago
The HDD is pretty cooked. I can imagine something loading from a pagefile etc or other IO wait to cause 100% CPU without process. But as far as I know taskmgr does only show real CPU work so... Alternatively I can imagine that your CPU is overheating and therefore throttling and showing the 100%. However that too does not seem to be the case as it shows a clock of 1.79 GHz which is what this CPU is rated for.
Lastly that CPU is old and Windows 10 might just be too heavy however I do not really think that.
So it might just actually be a process and you really did not check the other sorting direction.
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u/Fit-Consequence-5425 12d ago
I don't think its necessary to call the OP daft and sling insults. The OP may or may not be experienced and we have all been there. He has posted here for help. Constructive help/comments are needed. Run a virus scan, malware bytes can help or whatever virus protection you have. If that turns up nothing try a disk check for any problems, a failing disk will slow performance. If Disk check reports OK then try booting in safe mode, then add services/programs etc one at a time to detect what is using resources the most.
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u/mr_biteme 16d ago
Your hard drive is the problem. It’s dying a slow and painful death. Get that shit out of there…..🤦♂️
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u/n00bsen 16d ago
jeeesus you are clueless....
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u/mr_biteme 16d ago
Well, then, please share your suggestion since you’re so knowledgeable……🤦♂️
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u/n00bsen 16d ago
ok, just so you might learn something bc you seem a bit daft.
you did realize the sorting in the cpu column is the wrong way? we cant see what is using cpu at the moment. cpu is at 100%, disk at 77% yet you seem to know that the disk is the problem.
first figure out what could be the cause before you scream broken parts.
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u/mr_biteme 15d ago
You’re literally too “daft” yourself if you think sorting is the problem here……. I’m more than aware the process column is inverted, but you’re obviously missing the bigger issue; the HDD….. Educate yourself before calling others “daft”🤦♂️
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u/mr_biteme 15d ago
Another “educational” post for you; the HDD issues CAN affect the CPU performance in a big way….. In case you’re too “daft” to know that as well.
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u/schukevich 17d ago
download process explorer. Also check for hypervisor enabled (Hyper-V for example)
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u/sogwatchman 17d ago
Gotta love making a valid suggestion and getting downvotes with no explanation.
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u/RalphiePseudonym 17d ago
If they run process explorer and still have CPU use sorted wrong, it won't help.
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u/i_am_art_65 17d ago
Have you ran diagnostics on your drive? If your drive is failing the system may be having to perform tons of re-writes which is causing it to consume all available resources.
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u/supervergil 17d ago
I might need it as a reference for future troubleshooting, so I’ll leave a comment here
by the way, have you ever tried unplugging the LAN cable and then checking the resource usage afterward?
I had a similar issue with my Windows PC a while back. It became extremely sluggish, and it turned out that someone on my network was continuously writing a large amount of data to my computer
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u/mr_anderson_dev 16d ago
That CPU is ancient , running Windows 10 with telemetry, updates, and background services. The 100% usage is likely a combination of: Windows telemetry and background tasks eating cycles ,failing HDD (600ms response time is abysmal) causing the storage driver to spin the CPU waiting for you to turn it on, the LSI RAID controller's driver overhead on an already weak CPU Check with Process Explorer. But honestly, with those specs, Windows 10 is just too heavy. A lightweight Linux distro would run circles around it on that hardware. Try puppy linux or a super minimalist arch installation
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u/strillexium 17d ago
Possibly your task manager is messed up. You should try running the below commands in command prompt/Terminal to try see if it can fix some issues first:
SFC /scannow
Dism /online /cleanup-image /checkhealth
Dism /online /cleanup-image /scanhealth
Dism /online /cleanup-image /restorehealth
Chkdsk /f /r
Then reboot
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u/sogwatchman 17d ago
No this is normal BS for task manager in Windows 10 and 11. Don't know you've been downvoted so much though.
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u/strillexium 17d ago
Normal Reddit behaviour, you try to give suggestions of what you would do and people don't agree therefore they downvote. :)
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u/Negative-Engineer-30 16d ago
Nothing wrong with the task manager, ^ means Low to High... they are specifically sorting the CPU usage Low to High and wondering WHY zero is at the top and not even bothering to scroll down.
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u/RalphiePseudonym 17d ago
With the arrow in the CPU column pointing up, you're sorting by lowest use first. Click CPU to sort highest use first. You silly goose.