The file you are trying to open, 'MyFile' is in a different format than specified by the file extension. Verify that the file is not corrupted ...

Error:
The file you are trying to open, 'MyFile' is in a different format than specified by the file extension. Verify that the file is not corrupted and is from a trusted source before opening the file. Do you want to open the file now?

Scenario:
The above error message appears when trying to open an Excel file.

Reason:
The specified extension for the Excel file does not conform with actual version or format of the saved file. For example a CSV file is saved with XLS extension or an Excel 2007 file is saved with XLS extension instead of XLSX.

Solution:
Either extension or the format has to be corrected.