Remote Connection String to connect in MS SQL 2005

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<?xml version="1.0" encoding="utf-8" ?>

<configuration>
  <configSections>
  </configSections>
  <appSettings>
    <!--   User application and configured property settings go here.-->
    <!--   Example: <add key="settingName" value="settingValue"/> -->
    <add key="SqlConnectionString" value="Data Source=MINTU\SQLEXPRESS\SQLEXPRESS;Initial Catalog=EmiInventory;Integrated Security=False;user=sa;password=database"/>

  </appSettings>

  <system.net>
    <mailSettings>
      <smtp deliveryMethod="PickupDirectoryFromIis">
        <network defaultCredentials="true" host="localhost" port="587"/>
      </smtp>
    </mailSettings>
  </system.net>
</configuration> 

This is my config file. I am connected with a PC by LAN and the name of the PC is 'MINTU' and there is MS SQL Server 2005' name is 'MINTU\SQLEXPRESS' Thus why my connection string is :

<add key="SqlConnectionString" value="Data Source=MINTU\SQLEXPRESS\SQLEXPRESS;Initial Catalog=EmiInventory;Integrated Security=False;user=sa;password=database"/>

I am getting error:
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance is correct and the SQL Server is configured to allow remote connections.

But, I have already enabled remote and local connection on that PC and in my PC from SQL Server Surface Area Configuration. So, please help me if you have any solution.
Thank you.