已经第二次发现了，Windows 10 大版本更新后，用清理工具释放老版本所占据的磁盘空间时，会留下一个比较深的目录，无法删除。它的全路径通常是这样的：
C:\Windows.old\Users\{username}\AppData\Local\Packages\Microsoft.Windows.Cortana_cw5n1h2txyewy\LocalState..
请务必注意最后那两个点，正是无法删除的元凶。之前是如何删除的已经无法想起，今天突发急智，直接把 Ubuntu WSL 子系统打开，
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zhang@X230T:~$ cd /mnt/c/Windows.old/Users/zhang/AppData/Local/Packages/Microsoft.Windows.Cortana_cw5n1h2txyewy/ zhang@X230T:/mnt/c/Windows.old/Users/zhang/AppData/Local/Packages/Microsoft.Windows.Cortana_cw5n1h2txyewy$ ls -l total 0 drwxrwxrwx 1 zhang zhang 512 Oct 29 2017 LocalState.. zhang@X230T:/mnt/c/Windows.old/Users/zhang/AppData/Local/Packages/Microsoft.Windows.Cortana_cw5n1h2txyewy$ rmdir LocalState../ zhang@X230T:/mnt/c/Windows.old/Users/zhang/AppData/Local/Packages/Microsoft.Windows.Cortana_cw5n1h2txyewy$ ls -l total 0 zhang@X230T:/mnt/c/Windows.old/Users/zhang/AppData/Local/Packages/Microsoft.Windows.Cortana_cw5n1h2txyewy$ |
显然一举成功。