There may be keys where even the Administrator has no permission. For example, neither the Registry entry for Dektop Background,
HKEY_CLASSES_ROOT\DesktopBackground\Shell\Display, nor its subkeys and values, can be modified directly because the owner is TrustedInstaller.
- Open Regedit to 'Computer\HKEY_CLASSES_ROOT\DesktopBackground\Shell\Display' by copying the key and pasting into the location bar.
- Try to modify a value, e.g. change
Position from Bottom to Left.
- An error message is displayed.
- Right-click on the Key
Display and click Permissions...
- Click the Advanced button.
Note that the Owner of the key is TrustedInstaller. On an individual basis, it is trivial to take ownership of that key and change permissions so that Administrator (or a user) can modify the key in Regedit or load a .REG file for that key. However, if there are many such keys (e.g. you've exported an entire hive), then you'll need to run Regedit as user TrustedInstaller. There are applications such as PowerRun that enable you to run the CMD prompt or Regedit as TrustedInastaller, but double-check any download before using it. Another application for that purpose was flagged by many AV engines at VirusTotal.
Note also that with great power comes great responsibility. It is possible to mangle the Registry sufficiently to require reinstalling Windows. Regrettably, I must admit to learning this from experience. Image your entire drive before making major experiments.