Since you are using a USB disk, please use PS2ESDL v0.816... until v0.820 comes out. :)
I am trying to combine the PS2ESDL-I (iLink version) and regular/mainstream PS2ESDL series into one unified PS2ESDL release by v0.820, so you shouldn't be confused anymore after that. ;)
I did that, and never had to worry about having a device that can only be used with my PS2.
When I go to school, I can use USB 2.0. When I play on my PS2, I use the IEEE1394 port.