Microsoft Office Open XML is the new default file format for Excel 2007, PowerPoint 2007, and Word 2007. Why would Microsoft introduce a new file format with this release? No, not to make your life miserable. In fact, Microsoft Office Open XML is designed to make working with documents easier than ever before.

Imagine two versions of the same Excel spreadsheet—one is saved using the old .xls format and the other is saved using the new .xlsm format. Two spreadsheets identical in every way, except the .xlsm file is up to 75 percent smaller than its counterpart, it comes equipped with improved damage-recovery, and the "m" in the file extension lets you know that this spreadsheet contains macros before you open it. Throw in the inherent developer and data integration benefits of XML and you have a file format for the 21st century.

Standard Open XML file extensions end with an "x"—.docx, .xlsx, and .pptx. Open XML files containing macros, like the example above, end with an "m"—.docm, .xlsm, and .pptm. And don't worry; you can still save files in their original binary .doc, .xls, and .ppt formats for sharing with older versions of Office. However, a better option for users of Office 2000 SP3, Office XP SP3, and Office 2003 SP1 is to download the appropriate Open XML file converter from With the file converter installed, users can open and edit the new Open XML formats in their existing version of Microsoft Office. Keep in mind, new features of Office 2007 used in the original document creation will remain unavailable when working in these older versions.

If you can't see your file extensions in Windows Explorer, click Organize, then Folder and Search Options. Click the View tab and uncheck Hide extensions for known file types.

For more information on the Open XML file formats, visit the FAQ at

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