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The error 0xc1420115 you’re encountering indicates that the directory you’re trying to mount to does not exist. Here are a few steps you can take to resolve this issue:
Check the directory: Make sure the directory C:\Expand exists. If it doesn’t, you can create it using the command mkdir C:\Expand.
Check the WIM file: Ensure that the install.wim file is located in the C:\Test directory and that it’s not read-only. You can remove the read-only attribute from the file’s properties dialog.
Run the command again: After verifying the above points, try running the command again.
If the problem persists, you might want to consider using a different user account to execute the DISM command. If all else fails, you could use a tool like 7-zip to mount the .wim file.