Microsoft has added the new Office Open XML Formats to the following 2007 Microsoft Office programs:
• Microsoft Office Excel 2007
• Microsoft Office PowerPoint 2007
• Microsoft Office Word 2007
A compatibility pack is available to make sure that you can open and save Office Open XML Formats in earlier versions of Microsoft Office. You can install the compatibility pack on a computer that is running Microsoft Office 2003 programs, Microsoft Office XP programs, or Microsoft Office 2000 programs. When you install the compatibility pack, you can open, edit, save, and create files in the robust Office Open XML Formats.
Download compatibility pack here:
Read Microsoft information on the new format here: