소스는 이렇습니다 -__:;
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unit 1
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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  protected
   procedure WMMyShow(var M:TMessage);message WM_USER+4444;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation
uses
   unit2;

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
   Application.ShowMainForm := FALSE;
   Self.Visible := FALSE;
   with TForm2.Create(nil) do begin
      if IsWindow(Self.Handle) then OutHandle := Self.Handle;
      Show;
   end;
end;

procedure TForm1.WMMyShow(var M: TMessage);
begin
   Application.ShowMainForm := TRUE;
   Self.Visible := TRUE;
end;

end.
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unit 2
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unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm2 = class(TForm)
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private declarations }
  public
    OutHandle  :THandle;
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.FormClose(Sender: TObject; var Action: TCloseAction);
begin
   Action := caFree;
   if IsWindow(OutHandle) then PostMessage(OutHandle, WM_USER+4444, 0,0)
end;

end.