Thanks for the info. Yes, I'm sure you're right about the desirability of a later version of Office.
And yet, when I had OS X 10.5.7 installed, I had the Open XML Converter app as one of the "Open with..." options and it converted to doc with no difficulty.
The problem has arisen since I upgraded to OS X 10.6.8. Now, I don't even get the XML option.
(At some intermediate stage in the proceedings I had the XML Converter option and was able to convert to rtf).
As I indicated, I can receive docx documents via email. Reception is no problem. It's the conversion to my preferred doc format suddenly appears impossible.