i need a file downloader component for 开发者_开发百科Delphi . may you help me ?

Use the high-level URLDownloadToFile function:

uses UrlMon;

...

URLDownloadToFile(nil, 'http://www.rejbrand.se/', 'C:\Users\Andreas Rejbrand\Desktop\index.html', 0, nil);

Or, you could very easily write your own downloader function using the WinInet functions, something like

uses WinInet;

...

hInet := InternetOpen(PChar(UserAgent), INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
try
  hURL := InternetOpenUrl(hInet, PChar('http://' + Server + Resource), nil, 0, 0, 0);
  try
    repeat
      InternetReadFile(hURL, @Buffer, SizeOf(Buffer), BufferLen);

      ...

There is a lot of sample code here at SO. Use the search box above.

Update

I wrote a small sample. You might want to execute this code in its own thread and let it ping back every 10 kB or so, so that you can provide the user with some progress bar, for instance.

function DownloadFile(const UserAgent, URL, FileName: string): boolean;
const
  BUF_SIZE = 4096;
var
  hInet, hURL: HINTERNET;
  f: file;
  buf: PByte;
  amtc: cardinal;
  amti: integer;
begin
  result := false;
  hInet := InternetOpen(PChar(UserAgent), INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
  try
    hURL := InternetOpenUrl(hInet, PChar(URL), nil, 0, 0, 0);
    try
      GetMem(buf, BUF_SIZE);
      try
        FileMode := fmOpenWrite;
        AssignFile(f, FileName);
        try
          Rewrite(f, 1);
          repeat
            InternetReadFile(hURL, buf, BUF_SIZE, amtc);
            BlockWrite(f, buf^, amtc, amti);
          until amtc = 0;
          result := true;
        finally
          CloseFile(f);
        end;
      finally
        FreeMem(buf);
      end;
    finally
      InternetCloseHandle(hURL);
    end;
  finally
    InternetCloseHandle(hInet);
  end;
end;

You can also make this with Indy :

procedure DownloadHTTP(const AUrl : string; DestStream: TStream);
begin
  with TIdHTTP.Create(Application) do
  try
      try
        Get(AUrl,DestStream);
      except
        On e : Exception do
          MessageDlg(Format('Erreur : %s',[e.Message]), mtInformation, [mbOK], 0);
      end;
  finally
      Free;
  end;
end;

If you want quick download, you can also use Clever Internet Suite