Thanks Froggy!

I don't think my box supports RAID at all, and is only a single disc enclosure - with just the USB and eSATA connections on the back for expansion. I plugged a 320gb external HDD into it and it showed up, and let me put stuff on it and access it, but it shows as a folder in the NAS drive explorer view on the PC. Basically, what I have done with my NAS server is set up 4 folders (VIDEO, MUSIC, PICTURES, FILES) and then mapped them as network drives so they show up in the MY COMPUTER window as drives (like C, D etc) What I woul like to do is have more storage but continue to use these folders

On my downstairs PC, I didn't bother mapping the folders as drives, instead I just click in the NAS drive shortcut I made (which basically takes you to MY NETWORK PLACES > NAS DRIVE) which shows the 4 folders as just 4 folders. So, by adding more storage to my current NAS, I would end up having to use two folders to search for music, or two folders to see the video's etc.

I'd basically like to add more gb's, and then when the 400gb is full, stick stuff on the next HDD, then when I click on VIDEO's folder, all the vids are in there, not just the ones that are on the 400gb drive and have to navigate to a different folder to see the other vids....