From the good folks at macosxhints.com.
I always thought it might be helpful to use the OS X installation CD not only for the purpose of installing the OS, but to do some repairs which can’t be done when running from the hard disk. Fortunately, Apple has made this very easy. The only thing you have to do is to add the application(s) of your choice to the /Applications -> Utilities folder of the installation CD/DVD. After that, boot from the copy of the DVD, and in addition to the usual utilities, (for instance) the Terminal will appear in the list of commands you can execute if you added it before. I find that really useful, because if something goes wrong, the underlying Unix commands are most times able to fix it.