Started with an early version of Windows 10, tried the Fall/Creator edition, didn't like it (too many ads), rollback failed, reinstalled from from HD. Somehow, Windows.old got created, and in in it, two file entries are undeletable: SystemX64 and ProgramFilesCommonX64. Their names suggest they are symlinks to some obvious directories, but I keep getting told "The file cannot be accessed by the system" (sometimes the error number, 0x80070780 is mentioned as well) or "UNKNOWN MICROSOFT REPARSE POINT" when I try using SysInternal's junction app.
These entries seem to be junction points to directories that no longer exist. I've taken ownership, assigned every permission, tried the link shell extension, done various things with a live Linux distro (Cinnamon 18.1, IIRC?) -- nada. Well, not quite nada; I was able to rename and move the parent directory (to test if it were just pathnames being exceeded), but the real issues were still there.
In the grand scheme of things, the adware and simplified interface (ok, just the single-color title bars) bug me more, but this is pretty frustrating.
*Albeit by booting up under a different OS.
[Edits: I was a bit harsh on Windows, so I toned down the post.]