Microsoft Excel 2008

Did you know that files in Open XML Formats with the following file extensions are automatically zipped: .docx, .dotx, .xlsx, .xltx, .pptx, .potx, and .ppsx.

Documents, templates, worksheets, and presentations that you create in Office 2007 are saved with new filename extensions with an x or an m. For example, when you save a document in Word, the file now uses the .docx extension, instead of the .doc extension.

* The x signifies an XML file with no macros.