A hard drive is a special disk that is usually mounted permanently inside your computer's cabinet. You rarely see the hard drive, and almost never take it out. Hard drives are made of different material than floppies, and they are physically hard (although if you touched the actual hard surface, you would destroy it!) They spin much more quickly than floppies, and require much more precision. They are sealed inside a special case, and that is sealed inside the computer case. A hard drive has a much larger capacity than a floppy, and is much faster at saving and retrieving information. Modern computers frequently have hard drives with 500 MB or more of capacity. As this capacity grows, people are beginning to measure it in terms of gigabytes. Software programs are always becoming larger and taking more room on hard drives. It never takes long to completely fill up the capacity of a drive. If you can afford a large drive when you buy the computer, you won't be sorry, but you can usually add another drive or upgrade later.