The file format .docx (or as some like to call it “Satan’s extension) can be changed in Office 2007 to make it more compatible with other versions of Office. Going forward, as people and businesses update their software, this will be the preferred file extension. But if you work in an environment where backwards compatibility is a concern, you can make sure you save these files in the .doc format with a few clicks of the mouse. The other option would be to force those using older versions of Office to download a compatibility pack from Microsoft.
Change The Microsoft Word Default Save Format
The following will work the same in both Word and Excel. Open Word or Excel and click the Microsoft icon in the upper left corner. In the menu that opens look toward the bottom and click Word Options (or Excel Options). You will then see a preferences pane. Click Save then in the default save drop down list, specify you want Word to save in 2003 .doc format. Then close. The new settings will automatically save documents you create in a format that Office 2003 users can open.
If you would rather continue saving in the .docx extension, you can direct Office 2003 users to download the compatibility software from Microsoft. Download The 2007 Compatibility Pack Here .