Thought I might offer some suggestions - this is a real strange bird, to be sure.
Remove Avast completely. Let Windows Defender protect the PC for now.
Uninstall it from Add/Remove Programs. If you have difficulty uninstalling it, see here:
Avast Uninstall Utility | Download aswClear for Avast Removal
Please follow the instructions to boot the system into safe mode to effect the removal properly.
Let's make absolutely sure the system is not infected, so please run these two tools and post the logs using the "#" code box:
This will place a text file on the desktop called sfcdetails.txt. Please also post that file.Code:findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log >"%userprofile%\Desktop\sfcdetails.txt"
Let's see if there are any clues in here.
Graphics drivers could be an issue as well. Open Device Manager, expand the Display Adapters, select your graphics, right-click and select update driver>search online. See if anything installs that way. If not, go to the OEM support site, and check there as @essenbe suggests.