Sigh. !
Go into you bios of your motherboard.
If the motherboard is Uefi, select the advanced option.
In the bios look for the fast boot option and disable it, or turn it off.
Save the changes before you exit the bios.
Let the system restart, the moment it does, tap your F8 key on the keyboard in rapid succession.
When you get to the OS loading and boot options page.
Select safe mode.
Once windows has loaded to the desktop in windows safe mode.
Go to backup and restore of windows.
You will find a backup of the state of the system before the AVG update was applied.
Simply roll the system back with that restore point.