[cotseec]

ListBox1.Style:=lbOwnerDrawVariable; или какй другой OwnerDraw

Код:

procedure TForm1.ListBox1DrawItem(Control: TWinControl; Index: Integer;
  Rect: TRect; State: TOwnerDrawState);
var
  tmp:string;
begin
  tmp:=IntToStr(Index+1)+' '+ListBox1.Items.Strings[Index];
  ListBox1.Canvas.TextOut(Rect.Left,Rect.Top,tmp);
end;