Cargar la estructura de arbol del disco en un TreeView

private void Explor(TreeNode Node)
{
  try {
    Node.Nodes.Clear();
    string s;
    foreach (int s in Directory.GetDirectories(Node.FullPath)) {
    Node.Nodes.Add(Path.GetFileName(s));
  }
  } catch (Exception ex) {
    MessageBox.Show(ex.Message);
  }
}
 
private void BTN_Click(object sender, System.EventArgs e)
{
  TreeView1.Nodes.Add("c:\\");
  Explor(TreeView1.Nodes.Item(0));
}
 
private void TV_AfterExpand(object sender, System.Windows.Forms.TreeViewEventArgs e)
{
  TreeNode z;
  foreach (int z in e.Node.Nodes) {
    Explor(z);
  }
}