Laravel4 : The requested resource /admin was not found on this server

In folder public->admin place these files named

.htaccess  
favicon.ico  
index.php  
robots.txt 
web.config

like

and change your index.php file in admin folder
from this to

into this

hopefully it will solve your problem.
It worked for me.

It may that under public you have a folder named admin. That can be source of your problems.