http://channel9.msdn.com/ShowPost.aspx?PostID=73329
Word, Excel, and Powerpoint will get a new file format all based on XML.
The extensions will change from .DOC, .XLS, .PPT to .DOCX, .XLSX, .PPTX.
The new file format is actually enclosed in a ZIP file. Change the extension name to .ZIP and you'll be able to double-click and get access to all the pieces of the new format.
Блог Брайна Джонса (руководитель группы Microsoft Word).
