[NumLock]

Код:

var
  AFileStream: TFileStream;
  Data: array of Byte;
begin
  if not OpenDialog1.Execute then Exit;
  AFileStream:=TFileStream.Create(OpenDialog1.FileName, fmOpenRead);
  try
    SetLength(Data, AFileStream.Size);
    AFileStream.Read(Data[0], Length(Data));
    Memo1.Text:=Copy(PChar(@Data[0]), 1, Length(Data)); // это так...
  finally
    AFileStream.Free;
  end;
end;