Microsoft Office Word 2007 and 2010 save files in the Open-XML DOCX format. Older versions of Microsoft Office Word, such as Office 2003 and Office XP, use the DOC format. Reading DOCX files on a computer with an older version of Microsoft Office requires a free compatibility pack available from the Microsoft Download Center. Once the pack is installed, older versions of Microsoft Office will be capable of reading, editing and saving files in the newer DOCX format.
Visit the Microsoft Download Center and download the "Microsoft Office Compatibility Pack for Word, Excel and PowerPoint File Formats." Your download folder will contain a file called "FileFormatConverters.exe" when the download is complete.
Double-click on "FileFormatConverters.exe" to begin the installation process. The installer will guide you through the installation process. Click "Next" to proceed through the installation and "Finish" when the installation is complete.
Run Microsoft Office Word. Select "Open" from the "File" menu. In the file browser, click on the DOCX file you want to read and press the "Open" button. The file will open in Word.
Installing the compatibility pack will allows you to read DOCX files in Microsoft Office Word, XLSX files in Microsoft Office Excel and PPTX files in Microsoft Office PowerPoint.
Older versions of Microsoft Office need to be updated to the latest service pack before installing the Compatibility Pack. Run Windows Update if the Compatibility Pack does not install properly, then attempt a second installation.