Spec - This problem started before there was a sub-listing "Use Nested Virtualization".
In any case, since that sub-listing appeared, I have only either checked BOTH boxes "Enable Hardware-Assisted Virtualization" and "Use Nested Virtualization" or UNchecked BOTH boxes.
Also, each time I change the setting, I reboot, or it doesn't change anything. I know this because I cannot turn on XP Mode unless I reboot first.
The headline in this thread remains true. Avast blocks HAV unless its "Enable Hardware-Assisted Virtualization"is turned off.
Also, I am not using VBox. Wroot is trying to use it, a few posts above. I'm not the only one with this issue.
After three years, Avast has still not fixed the problem.