.NET HTTP POST Method - Cookies issue

I'm trying to use C# to login to hotfile.com. The first big issue was to overcome the 417 Error, which this line solved it:

System.Net.ServicePointManager.Expect100Continue = false;

Now I'm getting this error as I try to login using POST:

You don't seem to accept cookies. Cookies are required in order to log in. Help

I've tried several times, and googled around and I still can't login to Hotfile.com.. My code is this:

string response;
byte[] buffer = Encoding.ASCII.GetBytes("user=XX&pass=XX");

CookieContainer cookies = new CookieContainer();
HttpWebRequest WebReq = (HttpWebRequest)WebRequest.Create("http://hotfile.com/login.php");
WebReq.Credentials = new NetworkCredential("XX", "XX");
WebReq.PreAuthenticate = true;
WebReq.Pipelined = true;
WebReq.CookieContainer = cookies;
WebReq.KeepAlive = true;
WebReq.Method = "POST";
WebReq.ContentType = "application/x-www-form-urlencoded";
WebReq.ContentLength = buffer.Length;
WebReq.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1)";

Stream PostData = WebReq.GetRequestStream();
PostData.Write(buffer, 0, buffer.Length);
PostData.Close();

HttpWebResponse WebResp = (HttpWebResponse)WebReq.GetResponse();
Stream Answer = WebResp.GetResponseStream();
StreamReader _Answer = new StreamReader(Answer);
response = _Answer.ReadToEnd();
File.WriteAllText("dump.html", response);

Naturally, the user and pass would have your accounts values.

Here's a working example I wrote for you:

var cookies = new CookieContainer();
ServicePointManager.Expect100Continue = false;

var request = (HttpWebRequest)WebRequest.Create("http://www.hotfile.com/login.php");
request.CookieContainer = cookies;
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
using (var requestStream = request.GetRequestStream())
using (var writer = new StreamWriter(requestStream))
{
    writer.Write("user=XX&pass=XX&returnto=/");
}

using (var responseStream = request.GetResponse().GetResponseStream())
using (var reader = new StreamReader(responseStream))
{
    var result = reader.ReadToEnd();
    Console.WriteLine(result);
}