This is simply the aim of an InformationWeek article. NAS (Network Attached Storage) solutions exist to connect 1 Tera-byte (1000 Mega-bytes, dang!) of hard disk drives to your network, but you normally have to pay more than $1000 or 1000€.
Here, they show us how to build a DIY data server from a basic PC, a box big enough and four standard hard disc drives. The Operating System will be GNU/Linux for costs reasons, but it could be Windows as well and then beget a PC work station with an awful lot of data storage space.
Easy and cheap, this is the way to go!