There is no Registry entry for that (or anything else for BB).
BB stores its settings in preferences files. Intrface.bbw is the main one. You can save/load them from the Options menu. So you can save one called "Prefs with my Real Drums on my G drive", and then load that in when needed.

Updates dont mess with the preferences files, so you shouldn't lose those settings between updates.
Let me know if others are losing preferences between updates, as we would look into that.

To set the locations of RealDrums - Prefs-Real Drums Preferences
To set the locations of RealTracks - Prefs-Real Tracks Preferences

Have Fun!
Peter Gannon
PG Music Inc.