You can save XML on the server using the save method, as shown in the following excerpt:
<%
Response.Expires = -1000;
if (Request.ServerVariables("REQUEST_METHOD") == "POST")
{
// Load the posted XML data and save it to disk.
xmldoc.load(Request);
xmldoc.save(Server.MapPath("saved.xml"));
%>
Ok
<%
}
%>
The MapPath method resolves relative paths into the full paths required on the server.