how to open admin panel

[eluser]praveenarya[/eluser]
hi all,
as explained in the link i have created admin and my stucture is

codeigniter/
index.php
admin/
index.php
system/
application/
frontend/
......
admin/
.....

i am getting error failed to open stream 'D:\wamp\www\codeigniter\admin/system/codeigniter/CodeIgniter.php'

what should i change in my admin index.php file i think in line
require_once BASEPATH.'codeigniter/CodeIgniter'.EXT;

i tried adding ../ and also substr but no use

thanks in advance..