Hi Simranjeet,
I recommend getting root access of the system.
Enter grub at boot startup. change linux parameter and and add '1' to the line starting with word 'linux'. This will make you enter single user mode (root access). you can either change your root password or follow the instructions given below.
First create your script executable as follows : chmod +x <your script file name>
Second put it in the /etc/init.d directory: cp <your script file name> /etc/init.d/
Third create a symlink to /etc/rc.d directory: ln -s /etc/init.d/<your script file name> /etc/rc.d
And don't forget to add '#!/bin/sh' to the top of the file.
I hope it satisfies your problem.
Regards,
Bharat Wadhawan