Installation Errors - Backendpro

[eluser]Shiju S S[/eluser]

Fatal error: Class 'Site_Controller' not found in D:\xampp\htdocs\backendpro\system\application\libraries\Admin_controller.php on line 26

I used the following code in config.php to overcome the Fatal error: Class 'Admin_Controller'

Code:

function __autoload($class)
{
    if (strpos($class, 'CI_') !== 0)
    {
        if (file_exists($file = APPPATH . 'core/' . $class . EXT))
        {
            include $file;
        }

        else if (file_exists($file = APPPATH . 'libraries/' . $class . EXT))
        {
            include $file;
        }
    }
}

Now what? Please help