[Nyctos Kasignete]

Код:

procedure TForm1.Button2Click(Sender: TObject);
const
  _URL = 'http://www.google.com'; // можете заменить на своё
var
  WinDir: PChar;
  RunDLLPath: string;
begin
  GetMem(WinDir, MAX_PATH);
  try
    GetWindowsDirectory(WinDir, MAX_PATH);
    RunDLLPath := StrPas(WinDir) + '\system32\rundll32.exe';
    ShellExecute(Handle, PChar('open'), @RunDLLPath[1],
                 PChar('url.dll,FileProtocolHandler ' + _URL),
                 nil, SW_SHOWNORMAL);
  finally
    FreeMem(WinDir);
  end;
end;