Create a friend module called modForms.
Add a friend hashtable called Forms.

Friend Module modForms
   Friend Forms As New Hashtable()
End Module

In the Form_Load event for each form...

Me.Name = "FormName"
modForms.Forms.Add(Me.Name, Me)

This will add a reference in a central location accessible to all files in
the current project.

When you want to open a form...

Dim F As Form
If Not IsNothing(modForms.Forms("FormName")) Then
    F = modForms.Forms("FormName")
    If F.Visible = False Then
         F.Show()
    else
         F.BringToFront()
    End If
Else
    F = New FormNameObject()  
    F.Show()
End If

To make life easier, use the class name of the form for the Name property

NOTE:  This code only only creates a new instance of the form if it does not
yet exist.  The object variables serve only as references to the form.      

If the initialation code is in the New sub, or Form_Load, it will only run
once using this code.    

Greg,

Why you want all forms open, is this not a kind of spooiling performance and
memory?

In my idea for sure not OOP, more a kind of Modulair programming using Net.

Cor

If you decide to use my suggested code, you might want to add code to remove
the hashtable reference to the form in the form's closing event.

Private Sub Form1_Closing(ByVal sender As Object, _
   ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
       modForms.Forms.Remove("Form1")
End Sub

opened is supposed to be a single instance form? In other words, you
never want to have more than one "copy" of the form running at a time
right? If so I would recommend not keeping an internal list of opened
forms, as this approach is tedious and error prone and difficult to
maintain (in my opinion). Instead a much simpler approach would be to
just implement the Singleton Pattern on the form. My favorite
implementation has come from Jon Skeet who is a huge resource over in
the C# newsgroup. While his sample is in C# it should be easy enough
to convert (http://www.yoda.arachsys.com/csharp/singleton.html) but if
you need help just ask.

As far as the looping through all open forms question goes, Charlie
has already shown you how to use a hashtable to track the forms.
Though IIRC, doesn't VB 2005 have a My.Forms property that does this
automatically? I never use the My namespace since it isn't directly
available in the other .Net languages so I could be completely wrong.
Also, why exactly do you need to know all open forms?

Thanks,

Seth Rowe

How about trying to access a public property on the form?

If you can, it must be loaded, if not it will throw an error....

LFS