procedure Del; // 自定义过程
var
  Mutex: THandle;
begin
  Mutex := CreateMutex(nil, True, PChar(Application.Title));
  if GetLastError = ERROR_ALREADY_EXISTS then
  begin
    Application.MessageBox('程序已经在运行...','系统提示', MB_ICONERROR);
    ReleaseMutex(Mutex);   {释放资源}
    Application.Terminate;
  end;
end;

program Project1;
uses
  Forms, windows,
  Unit1 in 'Unit1.pas' {Form1};
{$R *.RES}
var Mutex:THandle;
begin
 Mutex := CreateMutex(nil,true,'one');  {第3个参数任意设置}
 if GetLastError <> ERROR_ALREADY_EXISTS then
 begin
  Application.Initialize;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
 end
 else
  Application.MessageBox('该程序正在运行！','提示',MB_OK);
  ReleaseMutex(Mutex);   {释放资源}
end.