In case you did not know, Office files that end with an (x), like PPTX, XLSX and DOCX, or an (m), like PPTM, XLSM, DOCM are actually ZIP files. If you rename these files to .ZIP, you can open them up and see all the component that make up what is now an the Office Open XML File Specification.
Years ago I was working on a project where we were programmatically modifying Office documents using the Open XML Toolkit. I got sick and tired of renaming the files to .ZIP, looking inside, making corrections as needed, and then renaming the file back. So I created this tool. I used it – a lot, and then… Well, I forgot about it.
I recently started working on a project where I needed to quickly get into the contents of an Office file to see if the changes being made were correct. I also needed to do light editing of the internal XML parts at times. And I seemed to remember doing all this before. I searched and search and then I found this old project. I have been using it a couple weeks now and figured it might be a good thing to share with the community. So I published it on GitHub:
https://github.com/davecra/OpenXmlFileViewer
The details for install and usage are in the README.md. Once installed, you will have to register it for each file type. Once setup, you would right-click on the file, select Open With and then click OpenXmlFileViewer.
You will be able to browse the parts like you would files in File Explorer:
Please let me know if you have any questions or issues.