Just a very quick note here (mostly a note to self) but I had a couple of folder from previous Windows 10 installations named Windows.old Windows.old(1), Windows.old(2) etc.

These folders should be removed when you use Disk Cleanup and select the “Remove previous Windows Installation(s)” option.


However I already did that and for some reasons a subfolder named C:\Windows.old\Users\<username>\AppData\Local\Packages\Microsoft.Windows.Cortana_cw
couldn’t be deleted and therefore the parent folder couldn’t be deleted.

I couldn’t delete them with Windows Explorer nor via the cmd prompt or PowerShell. Then I tried to use the \\? prefix and that worked: