If your Intel i5-8400 CPU is consistently running at 100% utilization on a Windows 11 system, it could be due to several reasons, and you may need to investigate further to identify the specific cause. Here are some steps you can take to troubleshoot and resolve this issue:

Check Task Manager:
Open Task Manager by pressing Ctrl + Shift + Esc or Ctrl + Alt + Delete and selecting Task Manager. Look for the processes or applications that are using a significant amount of CPU resources. This will help you identify the culprit.

End Unnecessary Processes:
In Task Manager, you can end any processes or applications that are using a lot of CPU resources and are not essential. Be cautious not to end critical system processes, though, as it can lead to instability.

Update Drivers:
Ensure that your CPU and graphics drivers are up to date. Outdated or incompatible drivers can cause high CPU usage.

Scan for Malware:
Malware infections can cause high CPU usage. Run a thorough malware scan using a reputable antivirus or anti-malware software.

Check for Windows Updates:
Make sure your Windows 11 operating system is fully updated. Microsoft often releases updates that address performance and security issues.....................