Word 2003 and QuarkXpress (.mcw)

After updating several of my users to Office 2003 they are now unable to save files with the extention .mcw because Word 2003 no longer list the extention as an Save option. User had this option available to them in Office/Word 2000. I checked Microsoft and QuarkXpress sites, but I don’t see an extention available for the QuarkXpress .mcw file format. Please advise if you know where, when or how I can get this plug-in and/or extention to support the .mcw file format

Thank you.