DISM corrupts images mounted to paths with short filenames

If you’ve been having trouble using DISM to update off-line Windows 7 images, make sure you aren’t mounting the image to a path which contains a short filename component.  In particular, note that the TEMP environment variable will contain a short filename component in Windows 2003 or earlier, and may contain a short filename component in later versions, depending on your username.

For example, if I were to create a folder on C drive named harryjohnston, this command would corrupt the mounted image:

dism /mount-wim /wimfile:c:\win7\install.wim /index:1 /mountdir:c:\harryj~1\mount

This wouldn’t:

dism /mount-wim /wimfile:c:\win7\install.wim /index:1 /mountdir:c:\harryjohnston\mount

If an image has been corrupted in this way, and is then used to install Windows 7 on a machine, the junction points on the target machine will retain the path of the mountpoint.  For example, the “Documents and Settings” junction point would point to c:\harryj~1\mount\Users instead of to c:\Users as it should.

Thanks to Joseph Conway from Microsoft, this issue has been filed as a bug and will hopefully be fixed in a future release of the WAIK (Windows Automated Installation Kit).  In the meantime, the workaround is obvious: use a different mountpoint. 🙂

Hope this helps.

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