One of my favorite Linux features is its endless adaptability as a cross-platform rescue tool, and my favorite rescue Linux of all is the excellent Gentoo-based SystemRescueCD. SystemRescueCD comes with every imaginable necessity:
And a lot more stuff you can read about at SystemRescueCD. With a SystemRescueCD or USB stick you can perform heroic rescues on any Linux, Unix, Mac OS X, Windows, and probably a number of lesser-known platforms as well. Yes, you can really fix these systems- you're not limited to the tired old reformat-reinstall dance that those big shot innovative vendors rely on.
SystemRescueCD comes with WindowMaker for folks who prefer a graphical environment to the command line, but it's pretty limited. It's good for running GParted, Leafpad, Firefox and Dillo, and for running multiple X terminals. It's nice and lightweight, so it should work even on frail old PCs and laptops.