Use Office 2007 Documents in Office 2003
If you haven’t upgraded to Microsoft Office 2007, you can use documents saved in this new version with the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats. The utility will allow you to open, edit, and save Office 2007 documents.
Its designed to work with Office 2003 and Office XP. The software will also work with the various Office 2003 viewers. You can get it at Microsoft’s Download Center.