What's the problem;
- that you can't login as root,
- that you can't edit (and save) menu.lst, or
- on reboot, you don't see any changes ???.

From a console/terminal enter: and post the output back here.

You're going to have to tell us what error message you get. Doing the following *will* allow you to edit the file you want to edit:

- Log in as root; type "root" in the username: field and your root password (if you have one) in the password: field. If you don't have one, try hitting Enter. You should see a # prompt.

- Now type ls -la /boot/grub

- You should see either grub.conf or menu.lst in the list.

- Type vi grub.conf or vi menu.lst. This will show you what's in the file. type "i" to edit, and when you're done and satisfied with changes you've made, hit Esc, then : (a colon), then type wq!

- If you can't edit grub or menu.lst, let us know what error message you get. If you have insufficient permissions, you could try chmod 777 <filename>.

You might battle with vi as an editor. If you have a kde dsektop then go K ->System and look for File manager on the menu. It will ask for root password. Once in there use the folder icon on the left and open up the directory tree and go to /boot/grub and look for grub.conf or menu.lst and use something like kwarite to edit the file.