Loading config file from XML
If you choose to manually parse the Xml document for loading only, I would prefer not to use the XmlDocument classes. They have a performance penalty. Instead use the XPathDocument and the XPathNavigator class to navigate trough your document.

    void ReadXml(XmlReader reader)
    {
        XPathDocument document = new XPathDocument( reader );
        XPathNavigator navigator = document.CreateNavigator();

        foreach (XPathNavigator nav in navigator.Select( "/*/*" ))
        {
            string keyValue = nav.GetAttribute( "SomeAttribute", navigator.NamespaceURI );               
        }
    }


Second, i would prefer not to manually parse XML at all but create strong-typed classes in your project that you can serialize and deserialize. That makes the usage of you configuration more easy.