Removeing unwanted files from numerous directories

Ok I am working on an app to delete unwanted files from a main directory and all sub directories under it. There are no files what so ever in the main directory there is just sub directories. I only want to keep 2 files a video file and another file.

Here is my code

Code:

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Imports System.IO


Public Class filedelete
    Dim dirPath As String
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Update_Form()

    End Sub
    Private Sub Update_Form()

        Dim dirs As List(Of String) = New List(Of String)(Directory.GetDirectories(dirPath))
        Dim filename As String
        Dim fileext As String
        Dim fullpath As String
        ' clear the listboxes to be updated
        ListBox1.Items.Clear()

        Dim ValidExtensions As String() = {".mpg", ".avi", ".wmv", ".mp4", ".nfo", ".jpg", ".png", ".gif"}

        Try
            For Each folder In dirs

                Dim txtFiles = Directory.GetFiles(folder)

                For Each currentFile As String In txtFiles
                    filename = currentFile.Substring(folder.Length + 1)
                    fullpath = folder + "\" + filename
                    fileext = Path.GetExtension(filename)

                    ' list of files to be deleted in this listbox
                    If Not ValidExtensions.Contains(fileext) Then
                        ListBox1.Items.Add(fullpath)
                    End If
                Next
            Next

        Catch ex As Exception
            MessageBox.Show("Unable to list files due to " & ex.Message)
        End Try
    End Sub


    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        ' File delete each item from the list box
        ' Text box to show each file being deleted.
        Dim l_index As Integer
        Dim l_text As String

        Try
            ' File delete each item from the list box
            ' Text box to show each file being deleted.

            For l_index = 0 To ListBox1.Items.Count - 1
                l_text = CStr(ListBox1.Items(l_index))
                File.Delete(l_text)
            Next
        Catch ex As Exception
            MessageBox.Show("Unable to list files due to " & ex.Message)
        End Try
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, _
                                  ByVal e As System.EventArgs) Handles Button1.Click

        Dim folderDlg As New FolderBrowserDialog
        Try
            folderDlg.ShowNewFolderButton = True

            If (folderDlg.ShowDialog() = DialogResult.OK) Then

                TextBox1.Text = folderDlg.SelectedPath

                Dim root As Environment.SpecialFolder = folderDlg.RootFolder
            ElseIf (folderDlg.ShowDialog() = DialogResult.Cancel) Then
                Return
            End If

            dirPath = TextBox1.Text
            Update_Form()
        Catch ex As Exception
            MessageBox.Show("Unable to list files due to " & ex.Message)
        End Try
    End Sub
End Class

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The list box is used to display the items only. There is going to be no selection from the listbox what so ever to delete the files. As I want all the files, that are not video files and one other file, in those directories deleted. (Sorry for the bold but wanted to stress this)

Couple of issues here.

1: It seems that when I select a folder from the file dialog it doesn't work all the time. I have created a bunch of sample directories with nested directories in there each with 5 or 6 sample files with 2 that are valid. The directories are named sample, sample(1) and so on to sample(7) each has 15 sub directories named sample1 ... sample15 each with a .avi .jpg a .sfv a .url a .txt file in them

2: I would like to remove each entry from the listbox during the file delete routine. Since I am not selecting anything from the list box and using that in the File.Delete() call I am unsure how to remove the corresponding entry from the list box.

3: It also seems now my file delete is not working either. That could be the issue with the list box getting the correct values.

4: In the file dialog If I cancel out of it and I test for the cancel key to be clicked and if it is then I return to the main form. How ever it takes 2 clicks of the cancel button to get it to return. How do I fix that?

5: In the file dialog box how can I get it to display all my drives under my computer instead of Desktop and everything below it. I do understand My Computer returns "" but is there anyway to get it to default to a drive in Computer