To meet the needs of users upgrading to the 2007, 2010 and 2013 Microsoft Office system, Microsoft offers updates and a compatibility pack for older versions of Office that enable a user to open and save 2007 Office files. Microsoft has added new file formats to Microsoft Office Word, Excel, and PowerPoint 2007, 2010 and 2013 to reduce file size, improve security, improve reliability, and enhance integration with external data sources.
To ensure that you can exchange documents between different Office versions, Microsoft has developed the Compatibility Pack for the Office Word, Excel, and PowerPoint 2007 File Formats.
If you are running Microsoft Office 2003 or Office XP, you can download and install updates so that you can open, edit, and save files that were created in newer versions of Microsoft Office, and also files that use Open XML Formats.