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 ...

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 ...

If the DAT file you're trying to open is text, you can convert the file into text in the Microsoft Excel program by first saving it as a CSV file. Right-click the DAT file on your PC and click "Open." ...