procedure FormCreate(...);
  begin
  exstyle := getWindowLong( application.hanle, GWL_EXSTYLE )
  end;
 
procedure FormShow(...);
  begin
  setWindowLong( application.handle, GWL_EXSTYLE, exstyle )
  end;
 
procedure FormHide(...);
  begin
  setWindowLong( application.handle, GWL_EXSTYLE, WS_EX_TOOLWINDOW )
  end;

unit SystemTray;
interface
uses Windows;
 
const
  WM_ICONTRAY = WM_USER +1;
 
  NIM_ADD     = 0;
  NIM_MODIFY  = 1;
  NIM_DELETE  = 2;
 
  NIF_MESSAGE = $00000001;
  NIF_ICON    = $00000002;
  NIF_TIP     = $00000004;
  NIF_STATE   = $00000008;
  NIF_INFO    = $00000010;
  NIF_GUID    = $00000020;
 
type
  tNotifyIconData = record
    size:            cardinal;
    wnd:             THANDLE;
    ID:              cardinal;
    flags:           cardinal;
    callbackMessage: cardinal;
    icon:            HICON;
    tip:             array[ 0..63 ] of char;
    end;
 
function Shell_NotifyIcon( message: cardinal; var pnid: tNotifyIconData ): BOOL;
  stdcall; external 'shell32.dll' name 'Shell_NotifyIcon';
 
implementation
end.

unit Main;
interface
uses
  ..., SystemTray;  // add the new unit to the end of your uses clause
 
type
  TMainForm = class(TForm)
    ...
  private
    // used when hiding the application from the taskbar
    f_ExStyle: cardinal;
    // used to add the application's icon to the system tray
    f_TrayIconData: tNotifyIconData;
    ...
  public
    procedure TrayMessage( var msg: tMessage ); message WM_ICONTRAY;
    ...
  end;
 
implementation
 
...
 
procedure TMainForm.FormCreate(Sender: TObject);
  begin
  // remember the proper display mode for the application
  f_ExStyle := getWindowLong( application.handle, GWL_EXSTYLE );
 
  // add the application icon to the system tray
  with f_TrayIconData do begin
    size            := sizeof( tNotifyIconData );
    wnd             := handle;
    ID              := 0;
    flags           := NIF_MESSAGE or NIF_ICON or NIF_TIP;
    callbackMessage := WM_ICONTRAY;
    icon            := application.icon.handle;
    strpcopy( tip, copy( application.title, 1, 63 ) )
    end;
  Shell_NotifyIcon( NIM_ADD, f_TrayIconData )
  end;
 
procedure TMainForm.FormDestroy(Sender: TObject);
  begin
  // remove the application icon from the system tray
  Shell_NotifyIcon( NIM_DELETE, f_TrayIconData )
  end;
 
procedure TMainForm.FormShow(Sender: TObject);
  begin
  // add the application to the taskbar if visible
  setWindowLong( application.handle, GWL_EXSTYLE, f_ExStyle )
  end;
 
procedure TMainForm.FormHide(Sender: TObject);
  begin
  // remove the application from the taskbar if hidden
  setWindowLong( application.handle, GWL_EXSTYLE, WS_EX_TOOLWINDOW )
  end;
 
procedure TMainForm.TrayMessage( var msg: tMessage );
  begin
  // show the form if the user left-clicks the tray icon
  if msg.lParam = WM_LBUTTONDOWN then show
  end;
 
...
end.

unit ChildForm;
 
interface
 
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs;
 
type
  TForm2 = class(TForm)
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form2: TForm2;
 
implementation
 
{$R *.DFM}
 
end.

unit MainForm;
 
interface
 
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  TrayIcon, StdCtrls, ExtCtrls;
 
type
  TForm1 = class(TForm)
    TrayNotifyIcon1: TTrayNotifyIcon;
    Timer1: TTimer;
    procedure Timer1Timer(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure TrayNotifyIcon1DblClick(Sender: TObject);
    procedure TrayNotifyIcon1Click(Sender: TObject);
  private
    { Private declarations }
    procedure createchildform;
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 uses ChildForm;
{$R *.DFM}
 
procedure TForm1.createchildform ;
var tempChildForm : TForm2;
begin
try
  tempChildForm := TForm2.Create(Self);
  tempChildForm.FormStyle := fsMDIChild  ;
 
 
finally
 
end;
end ;
 
procedure TForm1.Timer1Timer(Sender: TObject);
begin
  Timer1.Enabled := False;
  try
    createchildform ;
  Finally
  End ;
end;
 
procedure TForm1.FormCreate(Sender: TObject);
begin
 
   TrayNotifyIcon1.IconVisible := True;
 
end;
 
procedure TForm1.TrayNotifyIcon1DblClick(Sender: TObject);
begin
 show ;
end;
 
procedure TForm1.TrayNotifyIcon1Click(Sender: TObject);
begin
 hide;
end;
end.

interface
type
  TMainForm = class(TForm)
    procedure ApplicationActivate(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private:
    procedure SysCommandMessage(var Msg: TWMSysCommand); message WM_SYSCOMMAND;
  protected:
    procedure CreateParams(var Params: TCreateParams); override;
  end;
 
implementation
 
procedure TMainForm.ApplicationActivate( Sender: TObject );
  begin
  // Remove the application button from the taskbar
  // (and make sure it stays that way)
  ShowWindow( Application.Handle, SW_HIDE )
  end;
 
procedure TMainForm.FormCreate( Sender: TObject );
  begin
  // Keep the application button out of the taskbar
  application.OnActivate := ApplicationActivate
  end;
 
procedure TMainForm.SysCommandMessage(var Msg: TWMSysCommand);
  begin
  // Routing WM_SYSCOMMAND messages through here instead of the default
  // handler prevents Delphi from trying to create a taskbar button for the
  // application when minimized and maximized, which when combined with
  // ApplicationActivate would otherwise cause flicker.
  //
  // You could capture the SC_MINIMIZE command here and instead hide the
  // window, but you would have to make sure to let the user know that the
  // window was minimized to the system tray. Otherwise it will look like the
  // window just disappeared...
  //
  // You could also remove biMinimize and biMaximize from the mainForm's
  // BorderIcons, and trap the SC_MINIMIZE button to do nothing... For
  // example:
  //   if msg.CmdType <> SC_MINIMIZE then defaultHandler( msg )
  //
  defaultHandler(Msg)
  end;
 
procedure TMainForm.CreateParams(var Params: TCreateParams);
  begin
  // Add the main form's window button to the taskbar
  inherited CreateParams(Params);
  Params.ExStyle   := Params.ExStyle or WS_EX_APPWINDOW;
  Params.WndParent := GetDesktopWindow
  //  If I understand things correctly, if you comment out the last line then
  //  when you manipulate the window (say, restore it) other toplevel windows
  //  belonging to the application will also be affected (say, restored). But
  //  since this is an MDI application you shouldn't have any other toplevel
  //  windows... And I haven't played around with this any...
  end;