Can't Get SQL Authentication To Work With XP Pro SP2 In Very Simple Test Case

I'm trying to work my way through the steps of using a User Id and Password in a connection string.

I'm working with SQL 2005 Express, VS2005, in the development server. Got an error I can't get around...tried it several diffent ways on a slightly more complicated test site...no joy...so went to the MSDN tutorial...made the most "vanilla" test I could think of, and still can't figure it out.

I thought it would be simple enough that I could post the whole thing (below)

The test works fine with Integrated Security = True in the connection string. When I remove that phrase, I get the error:

{"CREATE DATABASE permission denied in database 'master'.
An attempt to attach an auto-named database for file E:MyPathApp_DataVSST_DB.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share."}

This occurs on the cn.Open statement below.

It gets past the login, so I know that the SQL User and password match up correctly.

==========================
<connectionStrings>
<add name="VSST_CN"
connectionString="Data Source=MyServerSQLEXPRESS;AttachDbFilename=E:MyPathApp_DataVSST_DB.mdf;User Id = VSST; Password=vsst123"
providerName="System.Data.SqlClient"/>
</connectionStrings>

=========================
Page Code Behind (no controls on page)
------------

Imports System.Data
Imports System.Data.SqlClient

Partial Class _Default
Inherits System.Web.UI.Page

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

Dim cn As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("VSST_CN").ToString())

Dim cmd As SqlCommand = New SqlCommand("SELECT COUNT(*) FROM VSST_Table", cn)
cn.Open()
Dim rdr As SqlDataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection)
rdr.Read()
Response.Write(rdr(0).ToString())


End Sub
End Class


=================
The DB

Table VSST_Table,
ID is int, primary key, identity
Field1, Field2, Field3, Field4, Field5 are varchar(50)

I added one record ("A", "B", "C", "D", "E") to the table through VS2005 Server Explorer

This shows up in Count = 1 from running the page when Integrated Security = True



=================
In SSMSE: (this is ALL I did, tried to use the minimum so not to confuse...)

I added the SQL Authentication Server level user "VSST" with the password "vsst123" (and the login works, as noted above)

I attach the .mdf

I add VSST to the Database Users, and give it db_owner

I add VSST to the Table with all permissions checked.

=====================================

I can't figure this out. This is a very vanilla test and I'm stumped. I'm about to give up on SQL Authentication entirely (at least for now), and just try to filter my inputs for SQL Injections...that's the only reason I have (at this stage in my biz plan) for needing SQL Authentication. On the other hand, I really don't like being this stumped on something that is so widely promoted as a common practice.

Any help on this would be greatly appreciated.

Thanks!