procedure TfrMain.ApplicationMinimize(Sender: TObject);
begin
  frMain.Hide();
  WindowState:=wsMinimized;
end;

procedure TfrMain.tiMainDblClick(Sender: TObject);
begin
  frMain.Show();
  WindowState:=wsNormal;
  Application.BringToFront();
end;

...............................
uses
  Forms,
  Main in 'MAIN\main.pas' {frMain},
  SqlInterface in 'SqlInterface.pas';  

{$R *.res}

begin
  Application.Initialize;
  Application.UpdateFormatSettings:=False;
  Application.MainFormOnTaskbar:=(ParamStr(4)='Tray');
  Application.CreateForm(TfrMain, frMain);
  Application.Run;
end.
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