The problem you have is because there is a nested relation ship in your XML file.
This perfectly legal as XML goes, but the class DataSet does not support this.
So what can you do?
Well, one option is to rename the root node from <BrowseNode> to <BrowseNodes> or similar.
Then you can read the XML file without any problem.
If this is feasible in this case depends on how you need to present the data.
This is one way to do it on the fly:
XDocument xDoc = XDocument.Load(Server.MapPath("~/node.xml"));
xDoc.Root.Name = "BrowseNodes";
DataSet ds = new DataSet();
ds.ReadXml(xDoc.CreateReader());