The
modified firmware, turns the connected USB HDD of the WDTV into a NAS. You could access it from any device on the network via SMB, FTP, NFS, etc... All you need is the modified firmware and a supported usb-ethernet adapter (like what the Wii uses for LAN). With this modified firmware, you can stream content from a device on the network.
From my understanding, you do not need a PC to be able to access your NAS via the WDTV. WDTV runs on some variant of linux, and once the modified firmware has been set up properly, it basically will communicate like a PC to your NAS.
Supported USB devices