Tried out the initial beta of Office Open XML Converter for converting Word 2007 docx files (XML format) to Word Mac 2004 format. Had to download a docx file from the Microsoft website, as have yet to receive any such files. Downloaded Word2007RTFSpec9.docx, a 880 K file about the RTC format specs for Word 2007. It took the Converter 2:24 minutes to convert the file. The resulting RTF file is 26.3 MB (!) in size. No trouble opening it in Word 2004. I saved it as a Word 2004.doc file, which was somewhat smaller than the RTF file, only 11.5 MB. It would appear that the Word 2007 XML format is a real space saver.
I also tried MacLinkPlus 16, which claims to have docx converters. Word could not open the RTF file translated by MacLimkPlus, saying the file was corrupted. I also converted the docx file directly to Word doc format with MacLinkPlus. This was opened by Word 2004. The text appeared to be the same as the files translated by Office Converted, by MacLinkPlus failed to align any of the images properly.