ktwebb is correct, it is a proprietary file system., ie. once you've formatted with the utility of the Linksys NAS device, you cannot then take the drive out and have it be readable on a PC for instance. You can of course re-format the drive for use with the PC, but not to transfer the data.
I have one of these same exact devices at home operating with a pair of external drives, one an 80 Gig, the other a 120 Gig. At the time I purchased it, it seemed like a good deal.. certainly cheaper than other NAS type devices, however, the old caveat that "you get what you pay for" is certainly true here. Support is practically non-existent. Lord help you if you forget the Administrator password to the device. 😱
It works fine for the purpose that I bought it for - to use for storing maps and patches for games at LAN parties, so others can get to it with ease, but I'm investing in a true rackmount NAS device for my home network PCs and servers.