Why does MalwareBytes turn off Defender on one PC and not the other?

[MamaBear2017]

This is weird. We have MWB on my Windows 8.1 PC and it runs along side Windows Defender. But we also have MWB on my sister's Windows 8.1 PC in the same house, and if we start MWB, it turns off Windows Defender and Defender can ONLY be turned on, if we turn off MWB

 

[RolandJS]

Did one Defender have real protection on and the other defender have real protection off? If yes, which defender was turned off?

 

[A Guy]

This is by design, Defender is set to disable itself if another AV program is registered to Windows Security Center.

If you install another antivirus product, Windows Defender AV will automatically disable itself and will indicate this in the Windows Security app. A setting will appear that will allow you to enable limited periodic scanning.

Windows Defender Antivirus in the Windows Security app - Windows security

To stop Malwarebytes from Disabling Windows Defender, open

Malwarebytes > Settings > Security

Scroll down and turn off Always register Malwarebytes in the Windows Security Center

A Guy

 

[RolandJS]

Folks, how do I register a 3rd party AV AM program using Windows Security Center?

 

[A Guy]

Is it a well known program? If so, try to re-register WMIUTILS.DLL

Press Win + X keys
Click on Command Prompt (Admin)
Type or copy-paste regsvr32 /u WMIUTILS.DLL
Enter
Reboot your PC
Press Win + X
Click on Command Prompt (Admin)
Type or copy-paste regsvr32 WMIUTILS.DLL
Reboot again

See if it shows now

There may be a more elegant way to do all that, but I've never used 8 or 8.1

A Guy