running a malware program on top of defender?

[stevesk]

First of all, there is a difference between Malwarebytes scanner(Not a real-time anti-malware) and Malwarebytes Realtime Anti Malware. If you are using the first one then there is no problem and you can smoothly use windows defender and Malwarebytes scanner.

But if you are using Real-time Antimalware Malwarebytes, then it might have the conflict with windows defender. And Unfortunately, most of the Malwarebytes are realtime Antimalware. It is not recommended to use more than one antimalware product.