To ensure that a Microsoft Office Excel 2007 workbook does not have compatibility issues that cause a significant loss of functionality or a minor loss of fidelity in an earlier version of Excel, you can run the Compatibility Checker. The Compatibility Checker finds any potential compatibility issues and helps you create a report so that you can resolve them.
Important When you work on a workbook in Compatibility Mode, where the workbook is in Excel 97-2003 Binary file format (BIFF8) instead of the new Office Excel 2007 XML-based file format (.xlsx), the Compatibility Checker is automatically run when you save a workbook.
Tip If available, you can click Fix to resolve simple issues. For more complex issues, click Help for more information.