What about the steps here? https://www.pgmusic.com/techfaq55.htm#166

166. Can I store the RealTracks and RealDrums on a different hard drive than the Band-in-a-Box® and RealBand program?
Yes. The "RealTracks" and "Drums" folders, which are normally located in your bb folder, contain all of the audio files. If you have all of the "Real files" released to date, these will be quite large. Moving them to a different hard drive allows you to free up disk space on your main hard drive. To move them, you can simply select those two folders and use Edit-Cut and Edit-Paste to transfer them to a different location. You may not need to move the folders; you may have selected a custom folder when you installed them originally, or you may have purchased the program on a USB hard drive.

Either way, you need to specify the location of the folders in Band-in-a-Box® before you will be able to use them, if they are located anywhere outside your main Band-in-a-Box® folder. To do this, go to Opt. | Preferences, and click on the [RealDrums] button. This opens the RealDrums Settings dialog (which can also be accessed by a button in the toolbar). Select the "Use a custom folder location" checkbox, then click the Select Folder button. Locate and select your Drums folder, then press OK. Alternatively, you could just type the path manually without using the Select Folder window.

Use the same procedure for your RealTracks folder (Opt. | Preferences | [RealTracks].