RE: When is the IXMLDOMDocumentType not read-only?

You are asking questions about how to work-around a limitation in a
particular implementation.  The appropriate forum for those types of
questions for MSXML is the microsoft.public.xml newsgroup
(http://msdn.microsoft.com/newsgroups/loadframes.asp?icp=msdn&slcid=us&newsg
roup=microsoft.public.xml&frame=true)

Off the top of my head, it would seem that you may be able to use the XSLT
capabilities of MSXML 3 to generate a DOM tree containing a document type
declaration.  It would be a kludge, but might work.

Again, please ask usage questions that are particular to a specific
implementation in the appropriate forum.