For some reason whenever I try to do a scan it says “some files could not be scanned” and all the files in the C:$windows.~BT cant be scanned. it says “error: File can not be accessed by the system (1920).” I tried uninstalling it and re-installing it but nothing works and I don’t know what to do. please help
well, you dont have to do anything as this does not mean they are dangerous
How do I handle files that avast! can’t scan? https://blog.avast.com/2014/02/28/how-do-i-handle-files-that-avast-cant-scan/
How to remove the Windows.old and $Windows.~BT folders after you upgrade Windows http://www.bleepingcomputer.com/tutorials/delete-windows-old-folder/