What settings automatically change permissions for registry keys?

Question

I ran the following registry hack to change my default .pdf reader from Microsoft Edge to Acrobat Reader DC:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.pdf\UserChoice]

"Hash"="ISdaXzJSA5s="
"ProgId"="AcroExch.Document.DC"

What I expected was for the registry hack to run and change the default pdf reader to Acrobat Reader, but I found that my account does not have the right permissions to change the registry with a script.

I am currently running an admin account on the computer. While I can manually change the permissions and run the script once, they automatically change back to what is shown moments later. What local settings automatically change permissions for registry keys like this?

Answer 1

It is "by design" for Windows 10 : so many applications were highjacking the registry on install or launch without asking for consent, that Microsoft decided that the only way to change associations is via the parameter interface.

The OS monitors the registry for these keys and replace any change not done thru the "Defaul App" dialog with the original value.

if you need to change that for a large number of computers, the official way is thru :

dism.exe /online /export-defaultappassociations:c:\temp\customfileassoc.xml

then (after prunning the xml file if you want)

dism.exe /online /import-defaultappassociations:c:\temp\customfileassoc.xml

Not that simple.