Abrir única instância

program Project1;

uses
Forms,
Windows,
Dialogs,
Unit1 in ´Unit1.pas´ ;

{$R *.RES}

Var HprevHist : HWND;
begin
  Application.Initialize;
  HprevHist := FindWindow(Nil, PChar(´TheProgrammer´));
  if HprevHist = 0 then begin
    Application.Title := ´TheProgrammer´;
    Application.CreateForm(TForm1, Form1);
    Application.Run;
  end else
  MessageDlg(´Você não pode executar outra cópia do aplicativo´, mtInformation, [mbOK], 0);