If you use Microsoft Office editions 2000 or 2003, you should be able to open work that someone else saved in the new, 2007 formats. Whereas Office 2000 and 2003 use .doc for Word documents, Office 2007 uses .docX. The following article explains how to read the new version files in Office 2000 or 2003.
Microsoft has provided the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats which can be accessed here. You will be prompted to save the compatibility software file on your local drive. The Compatibility Pack requires you to have Word, Excel, and PowerPoint 2000 or 2002 with Service Pack 3 or run the 2003 editions of those applications with SP1 or higher. Your operating system must be Windows 2000 SP4, Windows Server 2003, or Windows XP with SP1 or newer. You will also be automatically prompted to install the Compatibility Pack from Microsoft's site when you attempt to open a document created in Office 2007.
After installing the Compatibility Pack, you must restart your computer for the changes to take effect. After that you should be able to open Office 2007 files with older Office software. If you open an Office 2007 file in Office 2003, choosing Save will keep that file in the new format. The same is true for Word 2000. In Excel and PowerPoint 2000, however, you must choose Save As to keep an Office 2007 file from reverting to an earlier format