Run the following in powershell.
# This script will remove grouping from all possible views of the Downloads folder.
# The change is applied to the current user's profile only.
# Warning: ALL folder views (except Downloads grouping) will revert to Windows defaults!
# This is a minimal solution. To set ALL default folder views, use the free tool WinSetView.
$RegExe = "$env:SystemRoot\System32\Reg.exe"
$File = "$env:Temp\Temp.reg"