there are several hard disk servers on market, Imerge, Escient, Denon, Kenwood, Yamaha
just to name a few. These unit will stream your media throughout your home, some with on-screen listings of your complete libary; the new Escient Fireball can manager your DVDs as well. While these will interface with your PC, i'm sure you can accomplish the same thing with just the PC but i'm just not the guy to ask