How to Fix Modern Setup Host High CPU Usage?

To fix it, first restart your PC and let Windows try updating again. If the problem continues, run Windows Update Troubleshooter (Settings → Update & Security → Troubleshoot → Windows Update). You can also clear the SoftwareDistribution folder by stopping the Windows Update service and deleting its contents; this removes stuck update files.

Another tip is to make sure your Windows is fully updated and your drivers are current, as outdated drivers can slow down updates. Usually, the high CPU usage goes down once updates finish installing.