PHP ~ CodeIgniter URLs ~ remove index.php in url

my directory~

D:\wamp\www\CodeIgniter_1.7.2

add .htaccess
------------------------------------------------------------------------------------------
RewriteEngine on
RewriteCond $1 !^(index\.php|images|robots\.txt)
RewriteRule ^(.*)$ /CodeIgniter_1.7.2/index.php/$1 [L]
------------------------------------------------------------------------------------------

and these two urls get same result~
http://localhost/CodeIgniter_1.7.2/blog/qq/
http://localhost/CodeIgniter_1.7.2/index.php/blog/qq/

http://codeigniter.com/user_guide/general/urls.html