How to Make Excel 2007 Your Default Program. ... Excel documents may use the extension .xls, .xlsx or .xlsm for workbooks, or .xlt, xltx or .xltm for templates.

To fix the “Excel file format and extension don’t match” error, first check if the file extension matches its format. Try renaming the file with the correct extension (e.g., .xlsx for Excel ...

DAT files are files with an extension that isn't associated with a specific application or program and can be almost any type of file including video, media or text. Gaining access to the DAT ...

If Excel files are opening in Notepad on your Windows 11/10 PC, use these solutions to fix the issue: Check the file extension. Use the Open With option. Choose a default application for Excel ...