VB.NET - Carregar Treeview com as pastas existentes no computador

Carregando um objeto Treeview com as pastas existentes no diretório do computador.

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Me.TreeView1.Nodes.Add("C:")
For Each str As String In Directory.GetDirectories("C:")
Me.TreeView1.Nodes(0).Nodes.Add(str.Substring(3))
Next

End Sub