config.php

$config['installed'] = 'no';

routes.php

if (config_item('installed') == 'no')
{
$route["default_controller"] = "install";
}

core/MY_Config.php

config_path = APPPATH.'config/config'.EXT;
$this->database_path = APPPATH.'config/database'.EXT;
}

// --------------------------------------------------------------------

/**
* Update the config file
*
* Reads the existing config file as a string and swaps out
* any values passed to the function. Will alternately remove values
*
*
* @access public
* @param array
* @param array
* @return bool
*/
function config_update($config_array = array())
{
if ( ! is_array($config_array) && count($config_array) == 0)
{
return FALSE;
}

@chmod($this->config_path, FILE_WRITE_MODE);

// Is the config file writable?
if ( ! is_really_writable($this->config_path))
{
show_error($this->config_path.' does not appear to have the proper file permissions. Please make the file writeable.');
}

// Read the config file as PHP
require $this->config_path;

// load the file helper
$this->CI =& get_instance();
$this->CI->load->helper('file');

// Read the config data as a string
$config_file = read_file($this->config_path);

// Trim it
$config_file = trim($config_file);


// Do we need to add totally new items to the config file?
if (is_array($config_array))
{
foreach ($config_array as $key => $val)
{ 
$pattern = '/$config[\''.$key.'\']s+=s+[^;]+/';
$replace = "$config['$key'] = '$val'"; 
$config_file = preg_replace($pattern, $replace, $config_file);
} 
}

if ( ! $fp = fopen($this->config_path, FOPEN_WRITE_CREATE_DESTRUCTIVE))
{
return FALSE;
}

flock($fp, LOCK_EX);
fwrite($fp, $config_file, strlen($config_file));
flock($fp, LOCK_UN);
fclose($fp);

@chmod($this->config_path, FILE_READ_MODE);

return TRUE;
}

// --------------------------------------------------------------------

/**
* Update Database Config File
*
* Reads the existing DB config file as a string and swaps out
* any values passed to the function.
*
* @access public
* @param array
* @param array
* @return bool
*/
function db_config_update($dbconfig = array(), $remove_values = array())
{
@chmod($this->database_path, FILE_WRITE_MODE);

// Is the database file writable?
if ( ! is_really_writable($this->database_path))
{
show_error($this->database_path.' does not appear to have the proper file permissions. Please make the file writeable.');
}

// load the file helper
$this->CI =& get_instance();
$this->CI->load->helper('file');

// Read the config file as PHP
require $this->database_path;

// Now we read the file data as a string
$config_file = read_file($this->database_path);

if (count($dbconfig) > 0)
{
foreach ($dbconfig as $key => $val)
{

$pattern = '/$db[\''.$active_group.'\'][\''.$key.'\']s+=s+[^;]+/';
$replace = "$db['$active_group']['$key'] = '$val'"; 
$config_file = preg_replace($pattern, $replace, $config_file);

}
}

$config_file = trim($config_file);

// Write the file
if ( ! $fp = fopen($this->database_path, FOPEN_WRITE_CREATE_DESTRUCTIVE))
{
return FALSE;
}

flock($fp, LOCK_EX);
fwrite($fp, $config_file, strlen($config_file));
flock($fp, LOCK_UN);
fclose($fp);

@chmod($this->database_path, FILE_READ_MODE);

return TRUE;
}

// --------------------------------------------------------------------

/**
* Config status
*
* Checks the status of the config files and database connection
*
* @access public
* @return array
*/
function config_status()
{

$data['install_warnings'] = array();

// is PHP version ok?
if (!is_php('5.1.6'))
{
$data['install_warnings'][] = 'php version is too old';
}

// is config file writable?
if (is_really_writable($this->config_path) && ! @chmod($this->config_path, FILE_WRITE_MODE))
{
$data['install_warnings'][] = 'config.php file is not writable';
}

// Is there a database.php file?
if (@include($this->database_path))
{
if ($this->test_mysql_connection($db[$active_group]))
{
$this->session->set_userdata('user_database_file', TRUE);
}
else
{
// Ensure the session isn't remembered from a previous test
$this->session->set_userdata('user_database_file', FALSE);

@chmod($this->config->database_path, FILE_WRITE_MODE);

if (is_really_writable($this->config->database_path) === FALSE)
{
$vars['install_warnings'][] = 'database file is not writable';
}
}
}
else
{
$data['install_warnings'][] = 'database config file was not found';
}

return $data;
} 



}


/* End of file MY_Config.php */
/* Location: application/core/MY_Config.php */

dump SQL
remove install.sql then rename the new one to install.sql

Source
http://misael.org/2012/09/08/self-hosted-applications-installer-for-codeigniter/
https://github.com/misaelzapata/CodeIgniter-Installer/zipball/master
mine - https://skydrive.live.com/redir?resid=F6B936E6BD71BC1!5589