The MFC settings dialog is in the top window

 
BOOL CInput::OnInitDialog() 
{
	CDialog::OnInitDialog();

    ........
	/*
	 * 设置窗口为顶层窗口
	*/ 
    this->SetWindowPos(&wndTopMost,0,0,0,0,SWP_NOSIZE|SWP_NOMOVE);
	return TRUE;  // return TRUE unless you set the focus to a control
	              // EXCEPTION: OCX Property Pages should return FALSE
}