I'm trying to access a SQL database that is set up on a
Windows 2003 Enterprise machine on my network through my
VB.NET app.

I started with the following simple code just to make sure
I could access the database:

       Dim ConnectionString As String
       ConnectionString = "Password=" & DBPassword
& ";User ID=" & DBUsername & ";" & "Initial Catalog=" &
DBName & ";Data Source=" & DBServerHostname & ";"
       Dim DBConn As New SqlClient.SqlConnection
(ConnectionString)
       DBConn.Open()

I verified that everything was correct in the connection
string, etc., but I was getting SQL access errors, so I
decided to try to add a Data Connection in the Server
Explorer.

I can successfully add the server to the Server Explorer
and can access everything (e.g. event logs, performance
counters, services, etc.).  When I open the "SQL Servers"
item and click on the item underneath, a dialog pops up
asking for the username and password for the database.  
Even if I enter the correct info, I get an error
stating "Login failed for user '(username)'.  Reason: Not
associated with a trusted SQL Server connection.

What does that mean and how can I fix it?

I've had some experience writing and modifying existing
things like stored procs for existing databases but have
not worked before with creating a new database from
scratch and doing all this.  Below is what I did, just to
make sure I didn't do anything wrong on the SQL server:

-Created new database under 'local' under 'Microsoft SQL
Servers'
-Added new user to database with dbo rights
(authentication not based on Windows Authentication)
-Added new table to database
-Added columns to table (one is primary key)

Is there anything I missed there?

Thanks