I'm looking at setting up a virtual learning environment for my students using Moodle. I'm considering running it off a NAS box. I'd also like to use this box as a fileserver I can access over the net for iTunes and general files. I have 3 Mb broadband at the moment, and would like to run the box 24/7 so that it is independent of the laptop and desktop I have on the network at the moment.

What would be the best option? I'd like to avoid spending huge amounts of money, and would prefer a ready made Windows administratable (?) version.