I need to read contents of the file form a webservice. The file is on a mapped network drive

When I attemp to read the contents form ReportService.asmx file with the following code:
StreamReader stream = new StreamReader(@"T:\Timberline\WININST\network.txt");
string t = stream.ReadToEnd();

I get the following error:

System.Web.Service.Protocols.SoapException: Server was unable to
process request. --> System.IO.IOException: Logon failure: unknown
user name or bad password

How can I map the network drive and how can I setup the directory on the network so the Webservice does not have to logon?