windows 2003 server

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Hi ,

I am using windows 2003 and .net 1.1
I am trying to download word document.
this code works fine in windows 2000 .
but when i access in windows 2003 server
I get access denied (401)unautorized.

plz help
The following code is below:

Environment.CurrentDirectory = Environment.GetEnvironmentVariable("temp");

DirectoryInfo info = new DirectoryInfo(".");
CrmService service = new CrmService();

service.Credentials = System.Net.CredentialCache.DefaultCredentials;
string attachid =
"3BEAC1E6-2CDC-DB11-805A-00188B365618";//"4CA0E04F-1ADD-DB11-805A-00188B365618";//"3BEAC1E6-2CDC-DB11-805A-00188B365618";//"{61BB601D-C43F-4738-BD1F-AD22DC8E7F0E}";

string objecttypecode = "1070"; //SaleLiteratureItem
System.Net.WebClient myWebClient = new System.Net.WebClient();

myWebClient.Credentials = System.Net.CredentialCache.DefaultCredentials;

string url1 =
"http://dynamics/Activities/Attachment/download.aspx?AttachmentType=" +
objecttypecode + "&AttachmentId=" + attachid;

if(info.Exists)
{
myWebClient.DownloadFile(url1,info.FullName+"\\Fir st.doc");//(401
unauthorised)
}
Thanks and Regards
madhu