Unable to set default app for a filetype (Windows 11), any way to force it by other means?

How to Resolve Default App Settings for Specific File Types on Windows 11: A Comprehensive Guide

Understanding the challenge of setting default applications for specific file extensions can be frustrating, especially when Windows refuses to recognize or correctly associate certain formats. If you’ve encountered issues where Windows 11 does not respect your preferred app for a particular file type, such as a .mscz file (used by MuseScore), this guide provides strategies to resolve those problems effectively.

Problem Overview

In this scenario, the user aims to set MuseScore 2 as the default program for opening .mscz files. However, despite configuring the association via the “Open With” menu and the Default Apps settings, Windows defaults to an incorrect or outdated program—in this case, MuseScore 4. Attempts to uninstall or remove MuseScore 4 fail to fully eliminate the association, leaving Windows to suggest outdated executable paths and conflicting default settings.

Common Symptoms

• The .mscz files display an “Unknown file type” icon, despite being recognized as MuseScore Files.
• When opening such files, Windows prompts with the option to select MuseScore 2 as the default but does not enforce this association.
• The system continues to suggest or default to the nonexistent MuseScore 4 executable.
• Manual configuration via “Open With” and “Default Apps” doesn’t result in persistent changes.
• Attempts to remove residual entries through uninstallation and file deletion do not resolve the issue.

Step-by-Step Solutions

1. Reset File Association via Settings

2. Navigate to Settings > Apps > Default Apps.

3. Scroll down and select Choose Defaults by File Type.
4. Locate the .mscz extension.
5. Click on it and select MuseScore 2 from the list.

6. Ensure the change is saved and test opening an .mscz file.

7. Clear Corrupted or Stale Registry Entries

Sometimes, registry entries retain outdated associations. Modifying these can reset the default app behavior:

• Open Registry Editor (regedit.exe) as Administrator.
• Navigate to:
  HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.mscz
• Delete the key or reset values like UserChoice:
  • In UserChoice, delete the Progid value or modify it to point to the correct program.
• Be cautious: Registry editing can cause system issues