Missing A Needed Using Statement But Not Sure Which One

I'm trying to get my feet wet with creating a Sql Server project within VS 2005 and I have the using statements below present but when I compile I get errors stating that SqlContext, SQLPipe, and SQLCommand do not exist in the current context. What am I missing? Under the references node I have 3 references present (System, System.Data, and System.XML). What am I missing?

TIA

using System;

using System.Data;

using System.Data.Sql;

using System.Data.SqlClient;

using System.Data.SqlTypes;

using Microsoft.SqlServer.Server;