When you try downloading one of the Microsoft Office file types such as .docx, .pptx, .xlsx, the file may download as a .zip (Compressed Folder) file. This happens if the Office document MIME types are not registered in the web server you’re downloading the file from.
There is nothing much the user can do, apart from saving or renaming the file to the correct extension before opening it using Office.
If you had already downloaded the file (as .zip), simply rename (change) the extension accordingly. To do that, you’ll have to clear the Hide extensions for known file types check box in Folder Options.
If you’re a Webmaster and want to register Office Open XML File Formats on your server, visit the Office Resource Kit blog’s Register Office file format MIME types on Windows IIS servers article for detailed information.
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Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and he has been a Microsoft Most Valuable Professional (MVP) for 10 consecutive years from 2003 to 2012.