Edit the Grub boot loader Menu.lst in Ubuntu

Everytime I upgrade the Ubuntu package, I come across the choice of keeping the boot loader. I try to keep the menu.lst updated by accepting the changes.
This has a consequence: The default value on the menu.lst makes computer boot into another version of Ubuntu.
For example if I had XP/Vista OS as Third Option (selection 2) then after changes it would just start whatever is on the third option.
It could be Ubuntu 9.10, kernel 2.6.x.x.-generic

So, I need some way to edit the menu.lst or the boot loader or the grub menu editor.

How do I do it?

start the terminal
type:

gksudo gedit /boot/grub/menu.lst

or

sudo vi /boot/grub/menu.lst

remove the un-necessary items on the list.
save it and restart.