By installing the Compatibility Pack in addition to Microsoft Office 2000, Office XP, or Office 2003, you will be able open, edit, and save files using the file formats new to Word, Excel, and PowerPoint 2007. 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.
It’s about time! It’s hard to tell how well the compatibility works, but at least the files can be opened and edited at all.
Source: Bink.nu