Bit-tech have posted an excellent tutorial on “How to build a NAS box” which includes both the hardware aspects and the software, which in this case is FreeNAS.

“A NAS - or Network Attached Storage box is the easy and increasingly popular answer because you can simply drag and drop files to/from any PC… NAS boxes are a very low power way to store masses of data, while also giving everyone on the network access to that data.”