Hi,
I am experiencing the exact same error. I successfully installed DNN 4.3 the other day, but noticed there were no tables in my SQL database. It turned out that the data files were actually coming from some files in the DNN folder call "App_Data". I'm also using SQL Express 2005. Previously - when it worked - I had the following settings in my web.config - but this of course creates the files in the "App_Data" folder:
<connectionStrings>
<!-- Connection String for SQL Server 2005 Express -->
<add
name="SiteSqlServer"
connectionString="Data Source=.\SQLExpress;Integrated Security=True;User Instance=True;AttachDBFilename=|DataDirectory|Database.mdf;"
providerName="System.Data.SqlClient" />
<!-- Connection String for SQL Server 2000/2005 -->
<!--<add
name="SiteSqlServer"
connectionString="Server=(local);Database=dotnetnuke;uid=dba;pwd=dbapass;"
providerName="System.Data.SqlClient" />-->
</connectionStrings>
<appSettings>
<!-- Connection String for SQL Server 2005 Express - kept for backwards compatability - legacy modules -->
<add key="SiteSqlServer" value="Data Source=.\SQLExpress;Integrated Security=True;User Instance=True;AttachDBFilename=|DataDirectory|Database.mdf;"/>
<!-- Connection String for SQL Server 2000/2005 - kept for backwards compatability - legacy modules -->
<!--<add key="SiteSqlServer" value="Server=(local);Database=dotnetnuke;uid=dba;pwd=dbapass;"/>-->