Can Avast and Windows Defender both be active at the same time? In other words both proving real time Malware protection?
If you want them too they are compatible but I in all honesty Defender is rubbish and best disabled, it’s an absolute disgrace when it come to detections and is a total waste of resources ( Does that answer your question 
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Add Malwarebytes for secondary scans.
I used MalwareBytes once.
It killed my system. After running it the 1st time I could no longer start windows 7. Win7 went into major repair mode, didn’t work. Tried the advanced repair mode and went back to a restore point over two months old and still no joy.
Had to wipe the HDD and start with a whole new installation of Win7.
Seeing as how MalwareBytes is so popular I imagine I did something wrong when running it. All I know for sure is that it ran once. I did a reboot and W7 would never start up again.
Yes that does sound like you did something wrong. I have used Malwarebytes for years on XP and now also on Windows 8 with ‘never an issue’.
If all settings are left on “default” and nothing is changed then your experience is hard to understand, but I certainly can understand why one would never want to use it again. Having said that, I think there was something else going on. ???
I’ve not heard of Malwarebytes doing that before and I’ve been using it for years now and it’s recommended to all who show up here.