Removing old D:\Windows

It seems my old windows 7 directory (D:\Windows) is extremely difficult to remove. I already took ownership of all files (via Win10), but Microsoft, as usual, very aggressively hinders you in doing what you want to do.

How do I delete these files?! Even just opening an Administrative command prompt, using del *.* /s, doesn't work.

Thanks

The Take Ownership tool apparently couldn't take all files from the Windows 'root' in one big chunk. Applying it to each subdir individually worked just fine. Except for 1 file (see below)

Strange. Only file I can't remove is

D:\Windows\System32\Macromed\Flash\Flash64_21_0_0_182.ocx

meimeiriver said:

Strange. Only file I can't remove is

D:\Windows\System32\Macromed\Flash\Flash64_21_0_0_182.ocx

Now it's really solved. :) Needed to go thru quite a few hoops; but I needed to remove inheritance from it. Now it's gone.