Can I convert a msxml.IXMLDOMNode to XmlIntf.IXMLNode in Delphi?

You can create an instance of IXMLDocument and "attach" it to your IXMLDOMDocument. Here's a small example:

program msxmltest;{$APPTYPE CONSOLE}uses  SysUtils, ActiveX,  msxml, msxmldom,  xmldom,  XMLIntf, XMLDoc;function MSDOMDocumentToDOMDocument(const MSDOMDocument: IXMLDOMDocument): IDOMDocument;begin  Result := TMSDOMDocument.Create(MSDOMDocument) as IDOMDocument;end;function MSDOMNodeToDOMNode(const MSDOMNode: IXMLDOMNode): IDOMNode;const  NodeClasses: array[ELEMENT_NODE..NOTATION_NODE] of TMSDOMNodeClass =    (TMSDOMElement, TMSDOMAttr, TMSDOMText, TMSDOMCDataSection,     TMSDOMEntityReference, TMSDOMEntity, TMSDOMProcessingInstruction,     TMSDOMComment, TMSDOMDocument, TMSDOMDocumentType, TMSDOMDocumentFragment,     TMSDOMNotation);begin  Result := NodeClasses[MSDOMNode.nodeType].Create(MSDOMNode) as IDOMNode;end;function MSDOMNodeToXMLNode(const MSDOMNode: IXMLDOMNode; var OwnerDocument: IXMLDocument): IXMLNode;begin  Result := nil;  if not Assigned(MSDOMNode) then    Exit;  if not Assigned(OwnerDocument) then  begin    OwnerDocument := TXMLDocument.Create(nil);    OwnerDocument.DOMDocument := MSDOMDocumentToDOMDocument(MSDOMNode.ownerDocument);  end;  Result := TXMLNode.Create(MSDOMNodeToDOMNode(MSDOMNode), nil, (OwnerDocument as IXMLDocumentAccess).DocumentObject);end;var  Indent: Integer = 0;procedure ShowNode(const Node: IXMLNode);var  I: Integer;begin  Inc(Indent);  Writeln;  Writeln(StringOfChar(' ', Indent * 2) + 'NodeName: ' + Node.NodeName);  Writeln(StringOfChar(' ', Indent * 2) + 'NodeType: ' + NodeTypeNames[Node.NodeType]);  for I := 0 to Node.AttributeNodes.Count - 1 do    ShowNode(Node.AttributeNodes[I]);  if Node.HasChildNodes then    for I := 0 to Node.ChildNodes.Count - 1 do      ShowNode(Node.ChildNodes[I])  else    Writeln(StringOfChar(' ', Indent * 2) + 'NodeValue: ' + Node.NodeValue);  Dec(Indent);end;procedure Main;var  MSDOMDocument: IXMLDOMDocument;  XMLDocument: IXMLDocument;  MSDOMNode: IXMLDOMNode;begin  MSDOMDocument := CoDOMDocument.Create;  MSDOMDocument.load('C:\Program Files\Embarcadero\RAD Studio\8.0\ObjRepos\en\Code_Templates\Delphi\blockcomment.xml');  MSDOMNode := MSDOMDocument.documentElement;  // show all  ShowNode(MSDOMNodeToXMLNode(MSDOMNode, XMLDocument)); // you can reuse XMLDocument  Writeln;  // show author  MSDOMNode := MSDOMDocument.selectSingleNode('/codetemplate/template/author');  ShowNode(MSDOMNodeToXMLNode(MSDOMNode, XMLDocument));  Readln;end;begin  ReportMemoryLeaksOnShutdown := True;  try    CoInitialize(nil);    try      Main;    finally      CoUninitialize;    end;  except    on E: Exception do    begin      ExitCode := 1;      Writeln(Format('[%s] %s', [E.ClassName, E.Message]));    end;  end;end.