Note that Word 2010 uses the same file format as Word 2007.

If you are using an old document as the starting point when creating new ones, Word will suggest the format of the old document in the Save As dialog box. In the dialog, you can change the format by selecting "Word Document (*.docx)" for file type.

To verify that the format for new, unnamed documents (such as the blank document that displays if you start Word without double-clicking a file icon in Windows Explorer) is set to "Word Document (*.docx)," do the following: On the File tab, click Options. In the Save category, look at the "Save files in this format" option.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional