>I have a introduction form defined as top level which is shown during the startup. The same form is used for the about form from the help menu. The same form need to be top level at first and in screen for the about. But, that property is read only at run time. Any idea?

Store everything in the form, except the form as a container class. Have two forms now, one as top level for the start up with the container class and a second form, not top level, with the same container class. Should work and preserve OOP design.