将窗体显示在 PageControl 上

var

   AWinControl:TPageControl;

begin

  AWinControl  :=  PageControl1;

  if frmAbout = nil then Exit;

  frmAbout.ManualDock(AWinControl, nil, alClient);

  frmAbout.Align := alClient;

  frmAbout.Show;

end;

http://www.cnblogs.com/jxgxy/archive/2010/02/13/1668082.html