So you’ve just installed your second, or third, or ninth Linux distribution and it either didn’t recognize all your installs or you chose to skip that phase of the install. Of course you’d like to be able to boot all of these installs. Editing the grub.conf (or menu.lst) is an easy peasy procedure once you have an elementary understanding of the basic components.
If you are a Linux user and don’t understand the basic principles of Grub, then you are missing out on knowledge that will prove useful in the future. Most likely at a time when you least expect it and could really use it. This how-to explains everything to get you kick started.
Source: Tux Machines