Email this story Redundancy. By having two of everything, you can protect against something failing.
Banks generally have dual hard drives in all their computers, so everything is backed up.
If the main hard drive fails, the other takes over. Similarly, they've got backup power supplies so that, if one fails, the other takes over and devices stay on. You probably can't afford all that, but you can afford to back up your system. Copy everything that you can't live without from your computer to a Zip disk, Jaz disk, or other medium. It's like a power strip that has a battery inside it, so that if you have a brownout, blackout, or power surge, the computer will still get the right amount of electricity to keep running.