I added that add on from Microsoft. For you to create a fillintheform.doc on Word 2003, I fear you would need 2003.
I'll test it on my Office Word 2003 w/Microsoft's Docx addon if you wish. Just click on my name and drop me a line.
I created, for posting on a web site, a fill-in-the-blanks form in MS Word 2010 that works just fine for people who have Word 2007 or 2010 (.docx). Unfortunately, Word 2003 doesn't read the file properly. When I "save as" to 2003 (.doc), the form doesn't work. How can I convert the file so that people with Word 2003 can fill it in?