Dispose Managed Objects In 2008?

In My application, I have an MDI form. From MDI form I open all forms as child forms. I have implemented IDisposable for all large objects like file stream DB connection etc. In the Form_Disposed event I dispose all unmanaged objects. After the child form is closed, all unmanaged objects are disposed but managed objects (controls and form) are not disposed and still in memory. I find it from .Net Memory Profiler ([URL]).

So I have write code to remove all event handlers of all controls and form. Now, When form closed, dispose is called and all event handlers and controls are disposed, but controls and form are still in memory.