El Splash Screen se desaparece muy rápido

[eddg]

codigo del proyecto:

program Project2;

uses
Forms,
Unit1 in '..\..\..\..\..\Archivos de programa\Borland\Delphi7\Projects\nuevo\Unit1.pas' {principal},
Unit9 in 'iconos\Unit9.pas' {splashscreen};

{$R *.res}

begin

SplashScreen := TSplashScreen.Create(Application) ;
SplashScreen.Show;
SplashScreen.Update;
sleep(3000);
Application.CreateForm(Tprincipal, principal);
Application.Initialize;
Application.Run;
end.


codigo del FORM PRINCIPAL

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, Buttons, ImgList, ToolWin, ComCtrls, ExtCtrls,
ActnMan, ActnCtrls, Menus, Unit2, dblookup, ShellCtrls, Grids, Outline,
DirOutln, Spin;

type
Tprincipal = class(TForm)
...etc...
procedure ToolButton8Click(Sender: TObject);
....etc...

private
{ Private declarations }
public
{ Public declarations }
end;

var
principal: Tprincipal;

implementation

uses Unit3, Unit5, Unit9;

{$R *.dfm}

procedure Tprincipal.ToolButton8Click(Sender: TObject);
begin
close;
end;
...etc...

end.