Codenstuff.com

Imports System.IO 

Dim Dir as Directoryinfo = new Directoryinfo("Directory")
dim fo() as FileInfo = Dir.Getfiles("*.xml")
For each Fi as FileInfo in fo
Listbox1.items.Add(fi.Name)
Next

    Private Sub btnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSearch.Click
        Dim drive As String = Path.GetPathRoot(Environment.SystemDirectory)
        Dim files As String() = IO.Directory.GetFiles(drive, "*.xml", SearchOption.AllDirectories)
        '^ consider using a different thread if the UI becomes unresponsive.

        For i As Integer = 0 To files.Length - 1
            ListBox1.Items.Add(files(i))
        Next
    End Sub

    Private Sub btnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSearch.Click
        BackgroundWorker1.RunWorkerAsync()
    End Sub

    Delegate Sub addItem(ByVal item As String)

    Sub del_addItem(ByVal item As String)
        ListBox1.Items.Add(item)
    End Sub

    Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Dim drive As String = Path.GetPathRoot(Environment.SystemDirectory)
        Dim files As String() = IO.Directory.GetFiles(drive, "*.xml", SearchOption.AllDirectories)

        Dim d As [Delegate] = New addItem(AddressOf del_addItem)
        For i As Integer = 0 To files.Length - 1
            ListBox1.Invoke(d, files(i))
        Next

    End Sub

    Sub searchFolder(ByVal folder As String)

        Dim files As String()
        Try
            files = Directory.GetFiles(folder, "*.xml")
        Catch ex As Exception
            GoTo listFolders
        End Try

        For i As Integer = 0 To files.Length - 1
            ListBox1.Invoke(New addItem(AddressOf del_addItem), files(i))
        Next

listFolders:
        Dim folders As String()
        Try
            folders = Directory.GetDirectories(folder)
        Catch ex As Exception
            Return
        End Try

        For i As Integer = 0 To folders.Length - 1
            searchFolder(folders(i))
        Next

    End Sub

    Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Dim drive As String = Path.GetPathRoot(Environment.SystemDirectory)
        searchFolder(drive)

    End Sub