You should do your research. Microsoft has a translater to go BOTH WAYS between OOXML and ODF:
http://www.microsoft.com/Presspass/press/2007/feb0 7/02-01OpenXMLPR.mspx
...Translator enables conversion of documents from one format to the other and is available for anyone to download and use at no cost. When plugged into Microsoft® Office Word, for example, the Translator provides customers with the choice to open and save documents in ODF rather than the native Open XML format. The Translator may also be plugged into competing word processing programs that use ODF as the default format to open and save documents in Open XML. Microsoft Corp. announced its support for the open source project to build a technical bridge between Open XML and ODF in July 2006 to provide interoperability between formats. Since inception, it has remained among the 30 most active projects on SourceForge.net and has been downloaded more than 50,000 times...
