Перехватывать сообщения Windows до Application.Run

program Project1;

uses
  Forms,
  Unit1 in 'UNIT1.PAS' { Form1 },
  Messages, WinTypes, WinProcs,

{$R *.RES}

var
  OldWndProc: TFarProc;

function NewWndProc(hWndAppl: HWnd; Msg, wParam: Word; lParam: Longint):
  Longint; export;
begin
  { default WndProc return value }
  Result := 0;
  { handle messages here; the message number is in Msg }
  Result := CallWindowProc(OldWndProc, hWndAppl, Msg, wParam, lParam);
end;

begin
  Application.CreateForm(TForm1, Form1);
  OldWndProc := TFarProc(GetWindowLong(Application.Handle, GWL_WNDPROC));
  SetWindowLong(Application.Handle, GWL_WNDPROC, Longint(@NewWndProc));
  Application.Run;
end.