Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles MyBase.Load
        ' Form
        Me.WindowState = FormWindowState.Minimized
   End Sub
 
    Private Sub Form1_SizeChanged(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles Me.SizeChanged
        ' NotifyIcon zeigen
        If WindowState = FormWindowState.Minimized Then
            ShowInTaskbar = False
            NotifyIcon.Visible = True
        Else
            ShowInTaskbar = True
            NotifyIcon.Visible = False
        End If
    End Sub

MfG
Visual Studio .Net Team Suite 2008 - Meine neue lieblings IDE