Before you start
- A Windows PC
Method 1 Find the culprit
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Step 1: Open Task Manager
Press Ctrl + Shift + Esc. On the Processes tab, click the CPU column header to sort by usage.
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Step 2: Watch for a minute
Short spikes are normal. Look for something that stays high (e.g. 30–100%) for minutes.
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Step 3: Look it up
Right-click an unfamiliar process > Search online to see what it is.
| Process | What it is | What to do |
|---|---|---|
| Antimalware Service Executable | Microsoft Defender scanning | Let the scan finish; schedule scans when the PC is idle |
| Windows Modules Installer / Windows Update | Installing updates | Leave it running, then restart |
| SearchIndexer / Windows Search | Indexing files | Let it finish; limit indexed folders in Settings > Privacy & security > Searching Windows |
| Chrome / Edge | Too many tabs or a heavy site | Close tabs; use the browser’s own Task Manager (Shift + Esc) |
| System interrupts | Hardware/driver issue | Update drivers; unplug USB devices one by one |
| Unknown process with random name | Possibly malware | Run a full scan and Microsoft Defender Offline scan |
Method 2 General fixes
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Step 1: Restart
A restart ends stuck processes and finishes pending updates.
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Step 2: Update drivers and Windows
Install updates in Settings > Windows Update (including optional driver updates) and from your PC maker.
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Step 3: Disable heavy startup apps
In Task Manager > Startup apps, disable programs you don’t need running all the time.
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Step 4: Scan for malware
Open Windows Security > Virus & threat protection > Scan options and run a Full scan, then a Microsoft Defender Offline scan if anything looks suspicious.
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Step 5: Check power mode
On laptops, Settings > System > Power & battery > Power mode: Best performance runs the CPU harder; Balanced is fine for most people.
Troubleshooting
CPU is high but no process shows high usage
Click the Details tab and sort by CPU; some services are grouped. Or open Resource Monitor (search for it) for a detailed view.
It’s always 100% after startup for several minutes
Too many startup apps or an old hard disk. Disable startup apps and consider an SSD.
Frequently asked questions
Is 100% CPU usage harmful?
Not by itself: CPUs are built for it. But it makes the PC slow, noisy and hot, so find the cause.
Can I disable Antimalware Service Executable?
You shouldn’t; it’s your antivirus. Schedule scans for idle times instead.
Summary
Sort Task Manager by CPU to find the culprit. Let Windows Update, Defender and indexing finish, update drivers, disable heavy startup apps and scan for malware if an unknown process keeps the CPU busy.
