Windows Defender Cannot Be Activated After Uninstalling Comodo Anti Virus– Help Needed (Windows 10)

Hello Community,

I’m experiencing a problem with my Windows 10 laptop and hope to get some guidance. Official support is no longer available for my system, so I’m turning to the community for help.

Problem

Comodo Anti Virus /Internet Security / Internet Security Essentials had been installed on my laptop for a long time.

While Comodo was active, I could not load certain websites properly, and games like League of Legends would not run.

For this reason, I recently uninstalled Comodo.

After the uninstallation, the previously blocked websites and games work again.

Current issue:

My Windows Defender Antivirus cannot be activated.

In Windows Security, it shows:

“Virus & threat protection: Action required”

“The threat service has stopped. Start it now”

Clicking “Start now” only shows a loading indicator and then an “An unexpected error has occurred” message.

I have administrator rights, but Defender still cannot be activated.

Steps I’ve Tried

1. Registry checks

Path: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender

Checked entries like DisableAntiSpyware and DisableRealtimeMonitoring

Modifications often failed → access denied

2. PowerShell commands

Set-MpPreference -DisableRealtimeMonitoring $false → errors: “Parameter not found” or “Access denied”

Other commands like Set-ItemProperty or Set-Content → errors: “UnauthorizedAccessException” or “InvalidArgument”

3. CMD / SC commands

sc config WinDefend start=auto

Error: “SC Open Service Error 5 – Access denied”

4. Service check

Get-Service WinDefend | Select-Object Status, StartType → Status: Running, StartType: Automatic

Despite the service running, Defender cannot be enabled in Windows Security

5. System restore point created (For Comodo Revomal Tool)

Drive C: protection enabled

Backup created as a precaution

Insights / Analysis (Speculations)

After uninstalling Comodo, websites and games work again → this suggests that Comodo previously installed network filters or drivers that blocked them.

It is possible that remnants of Comodo (drivers, services, registry entries) are preventing Windows Defender from starting.

Firewall, App & Browser protection, and Exploit protection are active → partial protection, but Defender is not functional.

I am not certain if there are other causes, but based on my experience, it seems strongly related to leftover Comodo components.

Has anyone experienced similar issues where Defender remains blocked after uninstalling Comodo?

Are there safe methods to fully reactivate Defender without risking system stability?

Should I use the official Comodo Removal Tool to remove all remnants?

Are there alternative steps to try before using a removal tool?

I would greatly appreciate any guidance, tips, or steps I can try to get Windows Defender working again. Thank you in advance!