Problems with new MSDE installation

Hi,
I've a problem with connecting to my local MSDE installation. I'm using Windows XP Pro SP1 and logged in as administrator.

I've installed MSDE without further options (=setup SAPWD="password"). After that I installed some examples from Microsofts '101 Visual Basic.NET applications' using 'setup SAPWD="password" INSTANCENAME="NetSDK"'. Now I have 2 services running, 'MSSQLServer' and 'MSSQL$NetSDK'.

Then I followed the examples from a german book and created a Dataset etc. to access data from the Northwind database. The following line is created as SQLConnection1:

Me.SqlConnection1.ConnectionString = "workstation id=""COMPUTERNAME"";packet size=4096;integrated security=SSPI;data source=" & _
"""(local)\NetSDK"";persist security info=False;initial catalog=Northwind"
CType(Me.DataSet11, System.ComponentModel.ISupportInitialize).EndInit( )

When I right-click on the SQLDataAdapter1 and select 'Preview Data' everything works fine and I could see 9 Employee records. But when I then start the application it could not connect to the server. The error appears already in the first line, a simple connection call:
Me.SqlConnection1.Open()

Please could someone help me solve this issue? I already read several postings, here, on other sides, and on MSDN. I found information about a user account 'APSNET' which I am not allowed to implement due to security reasons. I also found the information about named pipes and TCP/IP, and so I added 'Network Library =dbmssocn' to the end of the SQLConnection-string, but with no success :-(

Many Thanks in advance for your support!Maybe try this type of connectionstring :

driver={SQL Server};server=ServerName;uid=sa;pwd=password;data base=Northwind