Nearly every desktop computer and server in use today contains one or more hard-disk drives. Every mainframe and supercomputer is normally connected to hundreds of them. You can even find VCR-type devices and camcorders that use hard disks instead of tape. These billions of hard disks do one thing well -- they store changing digital information in a relatively permanent form. They give computers the ability to remember things when the power goes out. Explore ComputersHow to Build a ComputerComputer Memory QuizPlanetGreen.com: Green LaptopsIn this article, we'll take apart a hard disk so that you can see what's inside, and also discuss how they organize the gigabytes of information they hold in files!