In Excel 2007, you can open files created in previous versions of Excel, from Excel 95 through Excel 2003.
In Excel 2007, you can open files that were created in previous versions of Excel, from Excel 95 through Excel 2003.
But what if you're the first person in your office to have Excel 2007? What if you need to share files with departments that don't have Excel 2007 yet? You can all share workbooks with each other. Here's how:
Old files stay old unless you choose otherwise. If you open a file that was created in a previous version, when you save that file and any work you do in it, the automatic setting in the Save As dialog box is to save the file in the original version's format. If it started in Excel 2003, Excel 2007 saves it in the 2003 format unless you say otherwise.
Newer features warn you if you save a file as older. When you save a file in a previous version's format, if any 2007 features are not compatible with the previous version, a Compatibility Checker tells you so.
For example, if you apply color to a header in Excel 2007, and then save the file in Excel 97-2003 format, the Compatibility Checker will tell you that previous versions of Excel do not have color for headers and footers, and that the header will appear as plain text.
Important When a new feature will not become available again if you save a file in an earlier format and then open it again in Excel 2007, the Compatibility Checker will warn you.
You can always copy newer files in newer format first. You can easily keep a 2007-format copy of the workbook. Just use Save As and tell Excel you want an Excel Workbook (*.xlsx). That copy of the file will contain all the Excel 2007 features.
Share documents between versions by using a converter. If you create a file in 2007 and save it in 2007 format, your colleagues who have Excel versions 2000 through 2003 (and the latest patches and service packs) can work in your 2007 files. When they click on your document, they will be asked if they want to download a converter that will let them open your document.
If the technical details interest you: The Excel 2007 file format is based on XML (Extensible Markup Language) and embraces the Office Open XML Formats. This is the new file format for Microsoft Office Word 2007 and PowerPoint 2007 also.