WPF Application fixed on Desktop - Opposite of topMost

Question

Is there a possibility to "fix" the WPF application on the desktop (like Win7 Gadgets)?

I have found some code which achieves this on Win XP but it is not working on Win7. It uses the user32.dll.

    public void DockStart()
    {
        IntPtr hwndParent = FindWindow("ProgMan", null);
        HwndSource hwndSource = PresentationSource.FromVisual(this.ParentForm) as HwndSource;
        SetParent(hwndSource.Handle, hwndParent);
        desktop = GetDC(0);
    }