You can buy the HDD with the FF11 Game, or with a linux kit. It does require a Network Adapter. If you look at the network adaptor you'll see the IDE Pins and Power Slot.
If you buy the linux kit you can copy MP3's Videos and other stuff to the PS2 through a home network, but you wont be able to play them during a game on during linux.
If you buy the linux kit you can copy MP3's Videos and other stuff to the PS2 through a home network, but you wont be able to play them during a game on during linux.