var
  Reg: TRegistry;
  buf : array [0..4] of byte;
  i: Integer;
begin
  Reg := TRegistry.Create;
  try
    Reg.RootKey := HKEY_CURRENT_USER;
    if Reg.OpenKey('\Software', True) then begin
      for i:=1 to 4 do buf[i]:=0;
      buf[0]:=1;
      Reg.WriteBinnaryData('Value', buf, sizeof(buf));
      Reg.CloseKey;
    end;
  finally
    Reg.Free;
    inherited;
  end;
  {...}
end;