Compatibility in Word 2007

In this screencast, Word program manager Jonathan Bailor demonstrates how Microsoft Office 2003 users can open and save Word 2007’s new default XML based formats natively.
Microsoft has adopted the Office Open XML file format, as the new default file format for Word, Excel, and PowerPoint
2007 to reduce file size, improve reliability, guarantee long term accessibility for archiving, and enhance interoperability with business solutions.
The Open XML formats are designed to enable the free exchange of data between documents and the systems that contain them. Finally, as one of the key design goals behind the Office Open XML formats was to maintain compatibility with the existing base
of Microsoft Office documents, solution providers can have confidence that their solutions will work not just with the documents of the future but with the billions of documents already in use today.
Related Links:
Jonathan Bailor’s Compatibility Pack post
Microsoft Office Word team blog
Brian Jones' OpenXML Formats blog
OpenXMLDeveloper.org
MSDN Word Developer Portal
MSDN XML in Office Developer Portal