To delete a node you need to remove it from its parent.
node1.ParentNode.RemoveChild(node1);
I really would recommend getting a book or something as these are fairly elementary questions you are asking.
You could try searching for a Xml .Net tutorial, like this one:
http://www.topxml.com/dotnet/ or
http://www.topxml.com/system_xml/default.asp
/- Sam Judson : Wrox Technical Editor -/