Just to give a little more background, and this may be something for
the ASP group but given that its XML I figured it could be handled
strictly in C# -

The code that calls the web service that returns XML string data that
is passed to the XmlDocument.LoadXml() method is all in code behind a
web page.

An input button on the default web page calls the webmethod with
parameters which returns the XML string which is now represented by
the memory stream (thanks Peter) which at this point is residing on
the web server. I'd like to "open" that document on the client PC
either in another instance of a browser (i.e. in IE with the default
markup) or in a blank page (preferred) that I have already added to
the  website.

This is the code I'm using so far that renders the XML doc in a text
box on the client with the formatting and indenting preserved:

{
       string a = Request.QueryString["ID"];
       string b = Request.QueryString["Date"];
       grrct.Service receipt = new grrct.Service();
       XmlDocument xdoc = new XmlDocument();
       xdoc.LoadXml(receipt.getIndividualReceipt(a, b));
       MemoryStream ms = new MemoryStream();
       XmlTextWriter writer = new XmlTextWriter(ms, Encoding.UTF8);
       writer.Formatting = Formatting.Indented;
       writer.Indentation = 3;
       xdoc.WriteTo(writer);
       writer.Flush();
       ms.Seek(0, SeekOrigin.Begin);
       TextBox1.Text = ret; //Shows elements and indentation
}

Since this is on a client PC, saving a local temp file is a bit tricky
from what I've read so far.