DOTNETDUKE SQL error 26

How should I setup the Database string and the database in sql 2005.

<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=;"/>
    -->

I am not sure how to attached the database the SQL server 2005 Database.mdf. It is also giving me issues.
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As well as this?
An error has occurred while establishing a connection to the server.  When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

My Server is Quincy.