Take a look at this and see if it helps:

boff.wordpress.com/.../editing-bootgrubmenulst-to-change-the-grub-\
boot-menu/

Depends on the release. On 9.04 and older versions edit the menu.lst
file found in /boot/grub/

in 9.10 I found it easer to just leave the extra, it will start using
the latest update.

How do I edit the boot process?

Open 'Synaptic' select 'installed software tab' enter linux in search
and mark for 'complete' removal all the old versions of the linux kernel
and headers, grub updates itself, simple ch' ch'!