VS 2005 Properly Handle All The Windows?

The app Im working on is dunning on an embedded xp machine. It recieves input from the serial port from an industrial process, and then a backgroundworker class calculates and updates the single form GUI with the results from the process. Very simple.Now, the customer want to allow automatic download of log files by an USB memory. The process should work like this:

1)User plug in an usb memory

2)SHow a virtual keypad (touch screen) where the user enter a security code

3)If code ok, show a 3 choice screen, if not ok show error message and allow the user to try again.

4) If user choose the "export all" button, this choose form will close and i display another form with a progress bar that show how all files are copied to the usb memory. When this process is complete, I will display teh form that says "remove the usb memory and press ok to restart the application.

As you see here lots of forms are created and disposed based on user choices. My biggest issue here is that I have no clear design pattern to work from.For example.. should I have this "chain" in the main gui form, or should I let each form create the next form. For example on the "select action" form, when I press export, should this form create and show the "copy progress" form, or should all forms be created and destroyed from the main gui form?

Also, such an issue like with the password. I put it as a constant on the main form, to avoid "magic numbers" in the code. And then I ran into problem because the "keypad" form is created on another thread and I can't access the costant on the main form, so I got a cross thread exception.Everything starts when an USB memory is connected. And the OnConnected eventhandler is running on a different thread than the main UI thread. how to design this chain of window creation/deletion is greatly appreciated. I show all forms with the SHowDialog because I dont want the user to be able to close the form unless he/she presses a button. And not by accident press somewhere else.