Set-FileAssoc.ps1 - a script to change Windows 10 file associations

What?

This script allows a user or an IT administrator to change user file associations in Windows 10.

Why?

User file associations in newer versions of Windows are normally protected from an unauthorized change, and therefore can only be set interactively through Settings app, or using a XML file pushed through GPO.

The XML method has several drawbacks:

• IT administrator has to keep track of any new associations when a Windows Feature Update gets released;
• if the computer is not in a domain, associations can only be set in a reference image, and as a result:
  • apps also have to be pre-built in your image;
  • once an user changes one of their file associations, it cannot be set back using the XML method.

A SetUserFTA tool has been made in 2017 to combat this limitation. However, it is also not a perfect solution:

• it only changes associations for the user that launched the tool;
• this is problematic if computers are managed by means of a remote configuration administration tool, like Ansible;
• workarounds to run SetUserFTA in different user contexts exist, but they are also not ideal;
• closed-source model.

For my personal use case (domainless network of Ansible-managed Windows 10 nodes with a "bleeding-edge" update policy), a different approach was needed, therefore, this script was made.

How?

1. Download the script;
2. Specify mandatory parameters - file extension and a ProgID (extension handler):
   • -Extension .pdf -ProgID SumatraPDF
   • -Extension .html -ProgID ChromeHTML
3. Set the user context in which this script should run:
   • current user only: -CurrentUser
   • all users: -AllUsers
   • specific users: -Users user1, user2
4. Run the script:
   • .\Set-FileAssoc.ps1 -Extension .pdf -ProgID SumatraPDF -CurrentUser
   • (shorthand version) .\Set-FileAssoc.ps1 .pdf SumatraPDF

Is that... legal?

This script is a product of reverse-engineering Windows binaries. Therefore, if your organization has to strictly adhere to Microsoft EULA, it may be problematic, legal-wise, to use this script, because:

• it circumvents the measures set in place by Microsoft to prevent tampering with file associations and user experience;
• it uses features that were implemented by reverse-engineering binaries that are "legally protected" from being reverse-engineered.

Consult your legal department for guidance.

Credits

Christoph Kolbicz for SetUserFTA: https://kolbi.cz