[NumLock]

Код:

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Button1: TButton;
    XPManifest1: TXPManifest;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

const
  EM_SETCUEBANNER = $1501;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
var
  Banner: String;
  buf: array [0..$ff] of Char;
begin
  Banner:=UTF8Encode('Введите логин');
  Utf8ToUnicode(PWideChar(@buf), PAnsiChar(Banner), Length(Banner));
  SendMessage(Edit1.Handle, EM_SETCUEBANNER, 0, Integer(@buf));
end;

end.