Issue with Codeigniter htaccess on local machine

Hi setup new code ignitior application on my local machine.

RewriteEngine on
RewriteCond $1 !^(index\.php|public|tmp|user_开发者_运维技巧guide|robots\.txt)
RewriteRule ^(.*)$ /index.php?/$1 [L]

This is .htaccess file content

and below is the config file content

$config['base_url'] = "http://localhost/myapp"; 
$config['index_page']= "";  $config['uri_protocol'] = "REQUEST_URI";

when i try to access application using http://localhost/myapp url gives ERROR 500

Error 500 localhost 10/05/11 20:43:26 Apache/2.2.4 (Win32) DAV/2 mod_ssl/2.2.4 OpenSSL/0.9.8e mod_autoindex_color PHP/5.2.3

So any idea what is the problem

[Wed Oct 05 21:50:22 2011] [alert] [client 127.0.0.1] C:/xampp/htdocs/myapp/.htaccess: Invalid command 'RewriteEngine', perhaps misspelled or defined by a module not included in the server configuration
[Wed Oct 05 21:50:33 2011] [notice] Parent: Received shutdown signal -- Shutting down the server.
[Wed Oct 05 21:50:33 2011] [notice] Child 4812: Exit event signaled. Child process is ending.
[Wed Oct 05 21:50:34 2011] [notice] Child 4812: Released the start mutex
[Wed Oct 05 21:50:35 2011] [notice] Child 4812: Waiting for 250 worker threads to exit.
[Wed Oct 05 21:50:35 2011] [notice] Child 4812: All worker threads have exited.
[Wed Oct 05 21:50:35 2011] [notice] Child 4812: Child process is exiting
Error in my_thread_global_end(): 1 threads didn't exit
[Wed Oct 05 21:50:43 2011] [notice] Parent: Child process exited successfully.
Error in my_thread_global_end(): 1 threads didn't exit
[Wed Oct 05 21:50:56 2011] [notice] Apache/2.2.4 (Win32) DAV/2 mod_ssl/2.2.4 OpenSSL/0.9.8e mod_autoindex_color PHP/5.2.3 configured -- resuming normal operations
[Wed Oct 05 21:50:56 2011] [notice] Server built: Mar  5 2007 11:23:00
[Wed Oct 05 21:50:56 2011] [notice] Parent: Created child process 4164
[Wed Oct 05 21:50:57 2011] [notice] Child 4164: Child process is running
[Wed Oct 05 21:50:57 2011] [notice] Child 4164: Acquired the start mutex.
[Wed Oct 05 21:50:57 2011] [notice] Child 4164: Starting 250 worker threads.
[Wed Oct 05 21:50:57 2011] [notice] Child 4164: Starting thread to listen on port 443.
[Wed Oct 05 21:50:57 2011] [notice] Child 4164: Starting thread to listen on port 80.

It seem obvious to me - just enable Apache's mod_rewrite.

http://www.astahost.com/info.php/Apache-Tutorial-Enable-Mod_rewrite-Windows_t11623.html