Thank you Beryllium9 ..
I have a single PC with two partitions. The distro I am using is RED HAT LINUX. I ve understood what you meant. Everything is clear except one thing. How do i get to the prompt after booting from bootable cd. do i have to type 'linux expert' or something like this to get on to the prompt where i could mount the partitions and nano that /mnt/whatever/grub/grub.conf and put a hash infronTof the line that is starting with 'PASSWORD'. I hope this is whatyou meant. Okie now one more thing just let me know two more things

1) can I still use 'vi' or I have to use 'nano' on the prompt that I'll get from the bootable cd.
2) what if i have installed the whole distro,but didnt entered a password for GRUB. But now after installation when its running I want to put a password on GRUB.What should I do then?
Thanx Buddy
Ommy