Microsoft is trying to get its Office OOXML format approved as an ISO (International Standard Organization) standard. As always, they try to set standards that benefit them and freeze out everyone else. When someone else tries to write to their standard, they change things in an incompatible manner. You can sign a petition against this here: http://www.noooxml.org/petition Here is a quote of the reasons from the site: Note: Office OpenXML (shortened OOXML) is neither open nor XML, nor is it a general "Office" file format, as it is specifically tailored to Microsoft Office 2007. Office OpenXML is NO WAY RELATED to OpenOffice.org, a free software office suite supporting the ISO office document standard ODF. A better, less confusing name would be "Microsoft Office Document ML" or something to that effect.