Original sentence: According to Microsoft, Office Open XML is backward compatible with Microsoft Office versions 2000, XP and 2003 using Microsoft Office Compatibility Pack
Edited sentence: , but Microsoft contends that the new file format, and the converters included with Office 2007 and subsequent versions of Office, will provide full backward compatibility with older Microsoft Office documents.Office Open XML isn't backward-compatible with versions of Microsoft Office prior to 2007 without the Microsoft Office Compatibility Pack.This new, XML-based file format represents a complete break with the previous Microsoft Office binary file formats