Avast not the cause. Had it on a new install upgrade from Win7
Had a second hand laptop to sell, but it didn't have a Win10 license.
Wiped it and installed Windows 7 x64
Installed latest Windows 10 from the Media Creation Tool
Setup froze twice with black screen, no cursor.
Eventually booted up to the point where it came up with the familiar desktop folder not accessible.
Gave up and sold it with Windows 7 instead.