Like many people, I don’t keep all of my data on one computer or device. I’ve got another machine that I dump less-used media to as my laptop doesn’t exactly have the largest hard drive in the world. Unfortunately, if you try to add a network drive to a Library using the GUI, it won’t let you. The back-end service, however, does support this functionality.
There’s a tool called Win7 Library Tool (aptly enough) that will let you add devices like that, so now you can view your video/picture (or whatever else) collection no matter where it is on your network. Huzzah!