procedure LoadFileToStringList(sl: TStringList; FileName: string);
const
  _BuffSize = 4096; // Cargamos en bloques de 4KB
var
  c: char;
  i: integer;
  R: integer;
  H: integer;
  s: string;
  B: PChar;
begin

  sl.Clear;

  B := PChar(AllocMem(_BuffSize + 1));
  H := FileOpen(FileName, fmOpenRead or fmShareExclusive);

  if H < 0 then
    raise Exception.Create('Error abriendo fichero' + #13#10 + '"' + FileName + '"');

  try

    repeat

      R := FileRead(H, B^, _BuffSize);

      for i := 0 to R - 1 do
      begin
 
        c := B[i];
 
        if (c in [#13, #10, #0]) then
        begin
          if (s <> '') then
            sl.Add(s);
          s := '';
        end
        else
          s := s + c;
 
      end;
 
    until R = 0;
 
  finally
    FileClose(H);
    FreeMem(B);
  end;
 
end;