Entire computers are often mistakenly referred to as a hard drive by those who lack computer savvy. The entirety of a computer box is a compilation of varied parts that provide power, processing and storage capability. These parts in unison form the computer and all of its capabilities, but the hard drive itself is merely a storage tank. All the data that the computer stores resides on the hard drive. This includes the operating system itself. Without a hard drive, the computer would have no software to boot to. All the applications you use are stored on the hard drive, as well as any personal files that you generate in your applications.
The speed which a computer boots is closely associated with the speed at which a hard drive can read and provide data to the disk controller on your motherboard. The boot process itself is nearly entirely comprised of data being read from the hard drive into the active memory of the computer. The faster the data is extracted from the disk surface, the sooner the computer will boot. Once the data is in random access memory, or RAM, it can then be processed and manipulated by the system. This data is kept in this volatile memory area until changes to it are made. Once that happen, the data is recommitted to the hard drive for permanent storage.
A hard drive contains fast moving parts, and is therefor limited in its overall lifespan. It is also susceptible to damage caused by movement or shock. Keeping your hard drive backed up is an absolute necessity to prevent damage loss in case of hardware failure. Backups can be kept on a variety of media types including DVD, Blu-ray, flash drives and other hard drives. An external hard drive is an excellent source of redundant storage space, as its capacity is comparable to your internal hard disk. Regular backups will keep your data safe from any form of hard drive failure.