I have asked several AI systems for help. The most common answer is:
"The error "Internal error: Failed to expand shell folder constant 'underdesktop'" typically occurs when an installation program cannot find or access the specified folder location on your system. This issue can arise due to various reasons, such as incorrect folder paths, missing environment variables, or permissions issues. Here are some steps you can take to fix this problem:
Run as Administrator:
Right-click the installer file and select "Run as administrator." This ensures that the installer has the necessary permissions to access all required folders.
Check User Profile Path:
Ensure that your user profile path (Desktop location) is correctly set. Sometimes, if the path is missing or corrupted, the installer may not be able to resolve the "underdesktop" constant.
To check this, open File Explorer, right-click on "This PC" or "Computer," and select "Properties." Then click on "Advanced system settings," go to the "Advanced" tab, and click on "Environment Variables." Ensure that the USERPROFILE and HOMEPATH variables are set correctly.
Create Desktop Folder Manually:
Navigate to C:\Users\YourUsername\ and ensure that there is a "Desktop" folder. If it does not exist, create a new folder named "Desktop."
Temporarily Change Installation Path:
If possible, during the installation process, change the installation path to a different directory that you know exists and is accessible.
Update Windows:
Make sure your Windows operating system is up to date. Sometimes updates can fix underlying issues with the system that might be causing the installation error.
Re-download the Installer:
The installer file may be corrupted. Try downloading a fresh copy of the installer from the GAOTD website and attempt the installation again.
Check for Software Conflicts:
Ensure that there are no other installations or programs running that might conflict with the installer. Close all other programs and try running the installer again."
Hope this helps.
Note: see also https://answers.microsoft.com/en-us/windows/forum/all/internal-error-failed-to-expand-shell-folder/ddedabd2-db20-4ccc-b35d-b7d6006f6309
https://www.reddit.com/r/SCCM/comments/kvsfvr/failed_to_expand_shell_folder_constant/?rdt=40710
has a.o. the suggestion to turn off your AV temporarily. I use that for giveaways like the one on June 26, 2024. That uses a special wrapper many AV's do not like.
https://github.com/WinMerge/winmerge/issues/354