ExtremeTech has published a new guide which shows you how to make an external HDD:
It's 2008, a year when even more PCs will be dedicated multimedia machines. Whether its movies, music, or personal photos taking up space, you will inevitably be faced with a decision when that hard drive fills up: Delete your precious multimedia or upgrade your storage options.
One quick and relatively easy way to get more storage is to build an external hard drive. Now is a great time to build one because hard drive space is pretty darn inexpensive. We found a Western Digital 750GB drive for only $249.99 (direct). So, really, the only thing stopping you from this little DIY project is a trip to Fry's.