For this purpose we have used recursive procedure.

VB.Net sample code

Imports System.IO

Public Class Form1

    Dim strrootpath As String

Private Sub btnmount_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnmount.Click

        FolderBrowserDialog1.ShowDialog()

        If (My.Computer.FileSystem.DirectoryExists(FolderBrowserDialog1.SelectedPath.ToString) = False) Then

            Exit Sub

        End If

        txtroot.Text = Path.GetFullPath(FolderBrowserDialog1.SelectedPath.ToString).ToString

        pathtree.Nodes.Clear()

        Dim str1 As String

        Dim str2 As String

        str1 = Path.GetFullPath(FolderBrowserDialog1.SelectedPath.ToString).ToString

        str2 = Path.GetDirectoryName(FolderBrowserDialog1.SelectedPath.ToString).ToString

        str1 = str1.Replace(str2 + "\", "")

        Dim RootNode = New TreeNode(str1)

        pathtree.Nodes.Add(RootNode)

        strrootpath = Path.GetDirectoryName(FolderBrowserDialog1.SelectedPath.ToString).ToString

        BuildDirectoryTree(RootNode, My.Computer.FileSystem.CombinePath(Path.GetDirectoryName(FolderBrowserDialog1.SelectedPath.ToString).ToString, str1))

    End Sub

    Private Sub BuildDirectoryTree(ByVal fromNode As TreeNode, ByVal basePath As String)

        Dim newDirectory As TreeNode

        Dim justTheSubdirectory As String

        pathtree.UseWaitCursor = True

        For Each oneDirectory As String In My.Computer.FileSystem.GetDirectories(basePath)

            justTheSubdirectory = My.Computer.FileSystem.GetName(oneDirectory)

            If (fromNode Is Nothing) Then

                newDirectory = pathtree.Nodes.Add(justTheSubdirectory)

            Else

                newDirectory = fromNode.Nodes.Add(justTheSubdirectory)

            End If

            BuildDirectoryTree(newDirectory, My.Computer.FileSystem.CombinePath(basePath, justTheSubdirectory))

        Next oneDirectory

        pathtree.UseWaitCursor = False

    End Sub

End Class

Explanation:

For this you need button with name btnmount, textbox with name txtroot, folderbrowsedialog with name  FolderBrowserDialog1 and treeview with name pathtree.

System.IO Namespace

The System.IO namespace contains types that allow reading and writing to files and data streams, and types that provide basic file and directory support.