Excel File Formats

You can change the default file save setting, to do that choose Office, Excel Options, then click the Save tab in the dialog box. From there a drop-down list will let you select the file format that you want to use aa a default. This is handy if you work in a mixed environment of Excel 2000, 2003 and 2007 versions. If your default is save as 2003 then everyone in your organization will be able to use the file.

Format	Extension	Description
Excel Workbook	.xlsx	The default Office Excel 2007 XML-based file format. Cannot store Microsoft Visual Basic for Applications (VBA) macro code or Microsoft Office Excel 4.0 macro sheets (.xlm).
Excel Workbook (code)	.xlsm	The Office Excel 2007 XML-based and macro-enabled file format. Stores VBA macro code or Excel 4.0 macro sheets (.xlm).
Excel Binary Workbook	.xlsb	The Office Excel 2007 Binary file format (BIFF12).
Template	.xltx	The default Office Excel 2007 file format for an Excel template. Cannot store VBA macro code or Excel 4.0 macro sheets (.xlm).
Template (code)	.xltm	The Office Excel 2007 macro-enabled file format for an Excel template. Stores VBA macro code or Excel 4.0 macro sheets (.xlm).
Excel 97- Excel 2003 Workbook	.xls	The Excel 97 - Excel 2003 Binary file format (BIFF8).
Excel 97- Excel 2003 Template	.xlt	The Excel 97 - Excel 2003 Binary file format (BIFF8) for an Excel template.
Microsoft Excel 5.0/95 Workbook	.xls	The Excel 5.0/95 Binary file format (BIFF5).
XML Spreadsheet 2003	.xml	XML Spreadsheet 2003 file format (XMLSS).
XML Data	.xml	XML Data format.
Excel Add-In	.xlam	The Office Excel 2007 XML-based and macro-enabled Add-In, a supplemental program that is designed to run additional code. Supports the use of VBA projects and Excel 4.0 macro sheets (.xlm).
Excel 97-2003 Add-In	.xla	The Excel 97-2003 Add-In, a supplemental program that is designed to run additional code. Supports the use of VBA projects.
Excel 4.0 Workbook	.xlw	An Excel 4.0 file format that saves only worksheets, chart sheets, and macro sheets. You can open a workbook in this file format in Office Excel 2007, but you cannot save an Excel file to this file format.