According to your web.config file, its assuming you are using

SQL Server 2005 Express because you uncommented that string

<!-- Connection String for SQL Server 2005 Express -->

However, you wrote: 

This is the initial install of DNN 4.3.4 and am running SQL 2005 Standard Version. 

If this is the case you must uncomment out the 2000/2005 strings and use those for connecting:

<!-- 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=ddosin;uid=sa;pwd=password;"
      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=ddosin;uid=sa;pwd=password;"/>
    
    <add key="InstallTemplate" value="DotNetNuke.install.config" />

Try utilizing these to strings instead.  comment out the 2kexpress strings with the <!--     --> tags.

-Mark Wilson

That did it (as he says red-faced)

Thanks very much for your help!

Gary