How to Open Office 2007 Files using Previous version of Office
If you are using Office 2003 (Word, Access, PowerPointor ect) and someone send you an attachment file that save in Office 2007 format, then you won't be able to open the file because Office 2007 file can't open with Office 2003 unless you download and installed Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint File Formats.
Click the following link to download and installed the Microsoft Office 2007 Compatibility Pack for Word, Excel, and PowerPoint File Formats.
http://www.microsoft.com/downloads/details.aspx?FamilyId=941B3470-3AE9-4AEE-8F43-C6BB74CD1466&displaylang=en
By installing the Compatibility Pack in addition to Microsoft Office 2000, Office XP, or Office 2003, you will be able to open, edit, and save files using the file formats in newer versions of Word, Excel, and PowerPoint. The Compatibility Pack can also be used in conjunction with the Microsoft Office Word Viewer 2003, Excel Viewer 2003, and PowerPoint Viewer 2003 to view files saved in these new formats.