Hint: Freeware to clean up old Windows SYSTEM disks [e.g., TakeOwnership.reg over TrustedInstaller & Administrator permissions)

This hint is written, as always, for two reasons:
a. To share with others what worked for me when I needed help, and,
b. To make it public so that others will _improve_ upon this knowledge
c. Such that it becomes even _more_ valuable, with your additions.

Freeware to clean up old Windows SYSTEM disks
[e.g., TakeOwnership.reg over TrustedInstaller & Administrator]

1. A Win10 desktop recently BSOD'd, so I needed to move some data off
the system HDD before attempting radical recovery methods...
o *Windows 10 BSOD indicates a hardware problem - but what hardware is the problem?*
https://alt.comp.os.windows-10.narkive.com/oL7PTNKu/windows-10-bsod-indicates-a-hardware-problem-but-what-hardware-is-the-problem

2. Normally (many times) I buy a new 3.5" HDD and install Windows clean
on it, but I have so may of those lying around from old previous
crashes that I simply filled a second HDD to the brim
(disks everywhere!) with a few of those old Windows SYSTEM disks
(some from Win7, Vista, and early Win10 era) which still had tons
of data so I didn't want to format them.

3. Of course, I ran the de rigueur "disk cleanup" method, which, IMHO,
is almost worthless; but, I did it anyway, even though it doesn't
remove all that much anyway.
Win+R cleanmgr{control+shift+enter}
o *What Is the $WINDOWS.~BT Folder, and Can You Delete It?*
https://www.howtogeek.com/268667/what-is-the-windows.bt-folder-and-can-you-delete-it/

4. As the system "Administrator", I deleted what I could, but the old
system Windows and ProgramData and ProgramFiles folders were giving
me trouble, even after running attrib globally:
C: attrib -s -h -a -r D:\*.*
Access denied - D:\autoexec.bat
Access denied - D:\bootmgr
Access denied - D:\BOOTNXT
etc.

5. Right clicking on each folder and messing with the permissions also
was a PITA and didn't work half the time anyway (for whatever reasons
the permissions were grayed out, even when I was "Administrator").
o *How to Take Ownership (Permission) of a File or Folder Manually in Windows?*
https://www.askvg.com/guide-how-to-take-ownership-permission-of-a-file-or-folder-manually-in-windows/

6. I then looked for freeware tools to allow me to delete old system
files, but as I was just beginning to survey these freeware tools,
I (repeatedly) ran into the "takeownership" registry option...
o *6 Tools To Take Ownership and Get Full Control Of Files and Folders*
https://www.raymond.cc/blog/easily-take-ownership-and-grant-full-control-permission-with-winownership/

7. Given take ownership context menus kept showing up as a solution
when I ran that survey, I found & downloaded this "TakeOwnership.reg",
file which, while it took forever to take ownership of every file,
eventually successfully allowed me to afterward delete what I needed
to delete on the old system disks (e.g., old Windows system folders):
o *Add Take Ownership Option in Files and Folders Context Menu in Windows*
https://www.askvg.com/add-take-ownership-option-in-file-folder-context-menu-in-windows-vista/

When writing this up, I looked a bit & found lots of seemingly similar
registry files, so I'm not sure what the differences are between them (if
any). Hence I simply ask those who already use "takeownership" registry
files to add your purposefully helpful input so that others benefit from
this information (particularly on clean removal of the registry keys when
done - which I haven't tried yet).
o *How to Add Take Ownership to Context Menu in Windows 10*
https://www.tenforums.com/tutorials/3841-add-take-ownership-context-menu-windows-10-a.html
o *How to Add ´Take Ownership¡ to the Right-Click Menu in Windows Explorer*
https://www.howtogeek.com/howto/windows-vista/add-take-ownership-to-explorer-right-click-menu-in-vista/
o *Take Full Ownership of Files & Folders Context Menu*
https://www.majorgeeks.com/files/details/take_full_ownership_of_files_folders_registry_hack .html
o *Add Take Ownership to Files, Folders & Drives Context Menu*
https://sumtips.com/tips-n-tricks/add-take-ownership-to-files-folders-drives-context-menu/
etc.

As always, please improve with your purposefully helpful adult suggestions.
--
The high cost of freeware is in finding & testing the best ones to use.