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High CPU usage when no applications are running on Computer
My computer shows extremely high CPU usage even when no applications are running, which causes the system to slow down significantly. Despite closing all programs and background processes, the CPU us...
Having no applications open does not mean the CPU is idle. Windows Update, Defender scans, third-party services, faulty drivers and malware can all run in the background. The first step is to identify the exact process using the CPU rather than ending processes at random.
- Press Ctrl + Shift + Esc, select More details, and open the Processes tab.
- Select the CPU column to sort from highest to lowest. Leave Task Manager open for two or three minutes and note the process that stays at the top.
- If it is Windows Modules Installer Worker, Windows Update or Antimalware Service Executable, connect the charger, allow it to finish for about 30 minutes, check for Windows updates, and restart the computer. Do not forcibly end these system processes.
- If a third-party program, updater or manufacturer utility is responsible, update or uninstall it. Also open the Startup tab in Task Manager and disable unnecessary startup applications.
- Run a malware check through Windows Security > Virus & threat protection > Scan options. Run a Full scan, followed by Microsoft Defender Offline scan if nothing suspicious is found but the usage remains high.
- To check Windows system files, open Command Prompt as administrator and run these commands one at a time:
DISM /Online /Cleanup-Image /RestoreHealth sfc /scannow - If System interrupts is using significant CPU, disconnect nonessential USB devices and update the laptop or motherboard manufacturer’s chipset, storage, network and audio drivers. Persistent System interrupts usage usually points to a driver or hardware problem.
- If the cause is still unclear, perform a clean boot: press Win + R, enter msconfig, open Services, select Hide all Microsoft services, and then select Disable all. Disable startup apps in Task Manager and restart. Re-enable the disabled items gradually to find the cause.
One important detail: a high value for System Idle Process is normal because it represents unused CPU capacity. The process name and its CPU percentage are the most useful information for determining the next step.