Hi Paul,
The Windows Imaging Format (WIM) is a file-based disk image format which is similar to other disk image formats. It helps to deploy Windows Vista and subsequent versions of Windows operating system family. To properly sort out your concern, we suggest that you post your question on our TechNet forums. The issue will be handled by our Windows 10 IT Pro audience to determine how you can properly open or read the .wim file on your computer. To do this, you may click the Ask a question button provided on this link.
If you have other questions, feel free to post it here in the Community.