The existence of something called "TrustedInstaller" is normal; the behavior I'm seeing isn't (well, I really hope so, at least).
Also: I've tried those methods to change ownership and, as said, they've made parts of the system break irreparably.
If I try the first method in your article, "1. Use File Explorer & Change Permissions to Gain Ownership.", at the step where I change the ownership of the C drive with my user, I receive 7 errors, 3 of which read "The process cannot access the file because it is being used by another process.", pointing at the following elements:
1) C:\swapfile.sys
2) C:\DumpStack.log.tmp
3) C:\pagefile.sys
4 other errors read "Failed to enumerate objects in the container. Access is denied." and they point at the following:
1) C:\Windows\System32\drivers\wd
2) C:\Program Files\Windows Defender
3) C:\Program Files (x86)\Windows Defender
4) C:\Program Data\Microsoft\Windows Defender\Platform
At the step where I check “replace all child object permission entries with inheritable permission entries from this object”, I receive 19 error messages, most of which (99%) read "Failed to enumerate objects in the container. Access is denied.", for instance applying to C:\bootmgr .
After this, the start menu, the search bar, the recycle bin and all elements in the bottom bar (Cortana, the calendar...even the notification manager) are unusable. They just don't do anything when I click on them.
The second method in the article fails instantly: "The current logged on user does not have ownership privileges on the file (or folder) "C:\"."
