At least in the Mac version, the Applications/Band-in-a-Box/Drums folder contains no audio files--just text files specifying the pattern. This is the same on the UltraPak disk (where the program works) and also on the laptop's disk. So Drums is set up different from RealTracks.

There must be m4a files somewhere for the drums, right? But where? Again, as far as I can tell everything's identical in the installation that works and the one that doesn't. So I can't tell how the UltraPak one is making sounds at all. Mysterious.