It may also help you to know how JRiver organizes your music. It's kind of a big topic, but here are some basics:
JRiver uses the tags in your songs to organize. So you can browse or search based on Artist, Album, Genre, Song Name, Year, etc. You usually wouldn't browse based on which disk the files are on. It looks like you have your disks organizes as Genres (Jazz, Rock, Classical, etc). You could use the Audio > Genres view to browse your music that way.
Or if you really wanted to, you could still browse based on File Location. Audio > Files . Then use the Location pane at the top to select the location and drill down from there.
You can also define your own views. You could build a view that's just Jazz for example. There are a lot of options if you want something specific. Otherwise, the default views are pretty useful!
Hopefully that will get you started.
Brian.