Save a workbook as an XLS file for use with an older version of Excel

To customize Excel to save a file in another format than *.xlsx, do the following:

   1.   On the File tab, click the Options button:

   2.   In the Excel Options dialog box, on the Save tab, choose the format you prefer in the list Save files in this format:

• Choose Excel 97–2003 Workbook if the file will be used by someone who has Excel 97, Excel 2000, Excel 2002, or Excel 2003,
• Choose Microsoft Excel 5.0/95 Workbook (the last one in the figure above) if the file will be used by someone who has Excel 5 or Excel 95.

Note: Don't forget to run the Compatibility Checker first to ensure nothing critical is lost when you save the workbook in an older format.