Fix Windows Defender Service Not Starting After Update - Resolve 'Port Already Allocated' Error in Windows Update-Resolve Windows Security Error 0x80073b01

Updated 2026-06-15 20:56:27macos-help

Fix Windows Defender Service Not Starting After Update - Resolve 'Port Already Allocated' Error in Windows Update-Resolve Windows Security Error 0x80073b01

Before changing system settings, save your work and note the exact error text so you can compare results after each step.

Extra verification checklist

Restart the affected app after changing permissions or configuration files.
Test the same workflow in a clean browser profile or a temporary user account.
Compare the result on another network if the error may be connection related.