From your question I am guessing that like myself you are new to Ubuntu, but
as you do not seem to have received a response I will try to help with what
I have just been through.



I found that the easiest way to change the boot order and other basics, was
by using 'Startup manager'.



'StartUp-Manager' is accessed via System > Administration > StartUp-Manager.
If it is not in your menu, install it via synaptic System > Administration
> Synaptic Package Manager. StartUp-Manager is in the 'universe' repository.



If you really want to edit the grub menu then you need to open a terminal
and enter: gksu gedit /boot/grub/menu.lst