"Network-attached storage (NAS) offers an alternative to traditional fileservers by creating systems designed specifically for data storage. A NAS box generally runs an embedded operating system (OS) rather than a full-fledged network OS, and it requires no monitor, keyboard, or mouse. One of the simplest NAS setups is Server Elements' NASLite.
"NASLite is a diskette-based Linux OS that can convert any PC into a dedicated fileserver. With it, you could create a NAS box out of an old 486 machine with 16MB RAM, a diskette drive, one to four IDE hard drives, and a network card..."