How to delete the remaining from Hard Disk

I have dual booting in my PC as Redhat Linux and Windows XP. I noticed 3 lines in GRUB while I boot. Out of this 3 lines through middle one I could go to Linux OS. Last line was Windows XP. 1st line not executing. Because of not executing and extra 1st one I intended to delete. One of my friend told me delete by command vi /etc/grub.conf
I give this command in Linux then I deleted lines of configuration out of two identical stuff. Now one configuration lines remaining. I have checked if I can reboot in both Linux and Windows XP. That is possible. Now in GRUB only 2 lines are there. I am not satisfied by only deleting configuration lines. I would like to delete that unncessary stuff from hard disk also. How can I recognise it and where is it? What is the command to go there. Would appreciate your response.