I am trying to upgrade our DNN 4.3 to 4.6.2, so then I will be able to upgrade it to 4.8. I had read that this is the way to go. I followed all the instructions I have gotten from this forum, but I get an error saying:   Error: Could not connect to database specified in connectionString for SqlDataProvider

I am running Sql Express 2005 on our Windows 2003 server. Here is part of my web.config file. I would appreciate any help! Thank you!

<configuration>  
  <!-- register local configuration handlers -->
  <configSections>
    <sectionGroup name="dotnetnuke">
      <!-- the requirePermission attribute will cause a syntax warning - please ignore - it is required for Medium Trust support-->
      <section name="data" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="logging" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="scheduling" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="htmlEditor" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="navigationControl" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="searchIndex" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="searchDataStore" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="friendlyUrl" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="caching" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="authentication" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="members" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="roles" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
      <section name="profiles" requirePermission="false" type="DotNetNuke.Framework.Providers.ProviderConfigurationHandler, DotNetNuke" />
    </sectionGroup>
  </configSections>
  <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=;pwd=;"
      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=;pwd=;"/>
 
    <add key="InstallTemplate" value="DotNetNuke.install.config" />
    <add key="AutoUpgrade" value="true" />
    <add key="UseInstallWizard" value="true" />
    <add key="InstallMemberRole" value="true" />
    <add key="ShowMissingKeys" value="false" />
    <add key="EnableWebFarmSupport" value="false" />
    <add key="EnableCachePersistence" value="false" />
    <add key="HostHeader" value="" />
    <!-- Host Header to remove from URL so "www.mydomain.com/johndoe/Default.aspx" is treated as "www.mydomain.com/Default.aspx" -->
    <add key="RemoveAngleBrackets" value="false" />
    <!--optionally strip angle brackets on public login and registration screens-->
    <add key="PersistentCookieTimeout" value="0" />
    <!--use as persistent cookie expiration. Value is in minutes, and only active if a non-zero figure-->