How do I properly uninstall a distro dual-booted with LL 2.0?

[m654321]

On a second laptop, I have LL 2.0 dual-booted with another distro (also ubuntu-based),
which I would like to remove, so that I only have LL 2.0 remaining on that computer
as my OS of choice.

I know that I need to do this properly, as merely deleting the distro's partition in Gparted
could mess up the grub screen spectacularly, and the computer generally.

I assume the procedure would be the same if I had any number of distros multi-booted
up to the maximum permissible number of 4 on any hard disk drive.

Grateful for any guidance on how to go about this. 

Regards
Mike