If you’ve got a Diamond Rio portable MP3 player, you can mount it as a file system in R4.5, using the tools in /optional/experimental/rio.
Once mounted, it appears as a regular disk volume to the Tracker, which means you can download files directly from web or FTP sites directly into the device, without having to use a separate Rio-loading utility. In other words, it’s easier to stock your Rio in BeOS than it is Windows.