hi all , here is an important and useful tip as to how one can protect the grub through password.
type " /sbin/grub-md5-crypt " on command line(without quotes )
you will be asked to enter the password and then re enter it. After that you will be provided with a md5 cncrypted password .. Copy it and paste it to the /etc/grub/menu.lst file at the top of the page just after the commented lines as:
password --md5 "encrypted password "
hope dats useful!