Problem with authentication to reporting server

Dear All,
I am trying to get data from reporting server and show it to client . 




        string url = "http://reports/ReportServer/Pages/ReportViewer.aspx?%2fLNA1123 - Repayment receipt (KB Subs)&P_REPAYMENT_DATE1=7/7/2010&P_GR_ACC_NO1=123123123&P_CLIENT_NAME1=els&P_BANK_CODE1=bank&P_BANK_ACCOUNT1=1212&P_BANK_BRANCH_NAME1=123&P_CREDIT_AMOUNT1=11&P_AMOUNT_IN_WORDS_CR1=asdasdasd&rs%3AFormat=MHTML";         HttpWebRequest req =(HttpWebRequest)HttpWebRequest.Create(ur ...