Public Class Form2
    Private Declare Function FindWindowEx Lib "user32.dll" Alias _
      "FindWindowExA" ( _
      ByVal hwndParent As IntPtr, _
      ByVal hwndChildAfter As IntPtr, _
      ByVal lpszClass As String, _
      ByVal lpszWindow As String) As IntPtr
 
    Private Declare Function GetDesktopWindow Lib "user32.dll" () As IntPtr
 
    Private Declare Function GetWindowText Lib "user32.dll" Alias _
      "GetWindowTextA" ( _
      ByVal hwnd As IntPtr, _
      ByVal lpString As System.Text.StringBuilder, _
      ByVal cch As Int32) As Int32
 
    Private Declare Function GetWindowTextLength Lib "user32.dll" Alias _
      "GetWindowTextLengthA" ( _
      ByVal hwnd As IntPtr) As Int32
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Try
            Dim allTitel As New Specialized.StringCollection
 
            Dim hwndDesktop As IntPtr = GetDesktopWindow
            Dim hwndChild As IntPtr = IntPtr.Zero
            Do
                hwndChild = FindWindowEx(hwndDesktop, hwndChild, vbNullString, _
                  vbNullString)
                Dim ret As Integer
                'Die Länge des Fenstertitels holen
                ret = GetWindowTextLength(hwndChild)
                If ret > 0 Then
                    'Den Titeltext des Fensters holen
                    Dim sb As New System.Text.StringBuilder(ret)
                    ret = GetWindowText(hwndChild, sb, ret)
                    Dim txt As String = sb.ToString
                    Debug.WriteLine("Fenster mit Text " & txt)
                    'Vergleich, ob der Text dem Gesuchten entspricht und ggf. 
                    ' merken
                    If txt Like "F*" Then
                        Debug.WriteLine("GEFUNDEN: " & txt)
                        allTitel.Add(txt)
                    End If
                Else
                    Debug.WriteLine("Fenster ohne Text")
                End If
            Loop Until hwndChild.Equals(IntPtr.Zero)
 
            Debug.WriteLine("ERGEBNIS:")
            For Each titel As String In allTitel
                Debug.WriteLine(titel)
            Next
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub
End Class