That's a functional workaround. I simply start the form minimized with
showintaskbar false. But that's not what I want to know. I'd like to be able
to simply toggle visible on and off, since opacity and windowstate have other
uses, but I don't see a way of starting a form with visible=false!

Post some code.

Then you have to write your own just-in-time compiler, your own managed
execution environment, your own memory management - and do not even declare
an Integer variable because the type is located in mscorlib.dll which is
part of the Framework that is, for the reasons mentioned, the minimum
requirement for every .Net application.

Back to your question... I copied some parts of a real-world app. Does this
help?

  Private Shared WithEvents NI As NotifyIcon
  Private Shared MainForm As Form1

  Shared Sub main()

     NI = New NotifyIcon

     Try
        NI.Visible = True

        Try
           MainForm = New Form1
           Application.Run()
        Finally
           NI.Visible = False
        End Try
     Finally
        NI.Dispose()
     End Try

  End Sub

  Private Shared Sub NI_DoubleClick(ByVal sender As Object, ByVal e As
System.EventArgs) Handles NI.DoubleClick
     ShowOrActivateForm()
  End Sub

  Private Shared Sub ShowOrActivateForm()
     If MainForm.Visible Then
        MainForm.Activate()
     Else
        MainForm.Show()
     End If
  End Sub

Armin