Connection To Ms Sql (login Failure!!!)

Im current working on this example in my ASP.NET Book. Creating a ADO.NET Shopping Cart for a Bookstore. A Database to store all books. Stored procedures (MS SQL 2000) parameterized queries (MS Access 2003) for all add, update, delete, and retrieve. Web Services that will handle all database interactions. Web Services Description Language (WSDL) Web References to the Web Services.Server-side classes that will connect the Web Services with the UI.

Im on the Web Services part and test the web service called sellerAdmin.asmx ive compiled and ran and the results of invoking the additem Web service i get an error mesg:
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<?xml version="1.0" encoding="utf-8" ?>
<string xmlns="http://tempuri.org/">System.Data.OleDb.OleDbException: Login failed for user 'sa'. at System.Data.OleDb.OleDbConnection.ProcessResults(I nt32 hr) at System.Data.OleDb.OleDbConnection.InitializeProvid er() at System.Data.OleDb.OleDbConnection.Open() at bookSource.sellerAdmin.ExecuteQuery(OleDbCommand QueryObject) in c:\inetpub\wwwroot\booksource\selleradmin.asmx.cs: line 53 at bookSource.sellerAdmin.addCat(String CAT_Name) in c:\inetpub\wwwroot\booksource\selleradmin.asmx.cs: line 196</string>
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The connection string in my c# code is this
this.sellerAdminConn.ConnectionString = @"Provider=SQLOLEDB.1;
Persist Security Info=False;
User ID=sa;
password= blank;
Initial Catalog=shopDb;
Data Source=singh";

Ive sorted the trusted SQL server connection problem in SQL Server enterprise manager(Properties->Tab to Security->Change SQL Server and Windows).

But it doesnt seem to recongised the user id and password, i think its using the windows local account. where do i go to sort this out?? plz help??

- did you add the ASPNET user to your db ?
- change the sa password to something other than blank (it's a security hole the size of Mt. Everest anyway ) and try again
- try using a different user then sa, you can still accomplish the same thing in an other user account if you give it enough permissions

if these don't work, just yell