New Word Document Format

Microsoft changed the document format used by the Word program in its Office 2007 for Windows and Office 2008 for Mac software suites. The old .doc file extension used by previous versions of the program has been replaced with .docx, which refers to the Office Open XML format. (This file format was developed by Microsoft and is not to be confused with the OpenOffice.org Productivity Suite, a set of open-source programs with their own formats.)
While people using the newer versions of Word can save their documents to a format that is compatible with older editions of the program, not everyone remembers to do so. You are not forced to upgrade to Word 2007 just to read these files, though, and there are a few ways to crack open a .docx file.
Microsoft offers its own compatibility pack that lets older versions of the Word program open and save files in Office Open XML format. An article in the company’s online knowledge base explains the process and provides a link to the compatibility pack for Word 2003, Word 2002 and Word 2000 at support.microsoft.com/kb/924074. (Some elements in a Word 2007 document may not convert properly, and an article at snipurl.com/1yos2 describes many of the things to look out for.)
For those using Word 2004 or Office v.X for Macintosh, Microsoft offers a free Open XML File Format Converter program that can be downloaded at www.microsoft.com/mac/downloads.mspx.
If you don’t want to use Microsoft’s solutions, the Web site at http://www.docx2doc.com/ offers both inexpensive Web-based file conversions and a standalone converter program. The Docx2Rtf program for Windows can also convert .docx files into rich text format (.rtf); the software is free and available to download at www.nativewinds.montana.com/software/docx2rtf.html.

Source: New York Times