Lets assume this question is talking about what you think is a Word docx or docm document.

You can firstly ensure it is a valid zip file by making a copy of the file and changing the file extension to .zip and verify if you can open and examine the structure of the file. Does this look similar to the same structure of another docx file that you can open?

You can also open Word first and use File>Open to navigate to the the document and then click the Open dropdown button and choose Open and Repair.

Finally, you can also try to recover the file by using an alternative tool such as OpenOffice which can be more fault tolerant in opening a corrupted file.

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Andrew Lockton
Chrysalis Design, Melbourne Australia