Yes, I had the same problem and still not certain how to resolve it.

I *always* install BIAB upgrade manually to my D: drive and every EXE I installed with this upgrade honored that convention, correctly installing to the D: drive.

But, when I got to the following three files,

playable_realtracks01_sforzando.exe
playable_realtracks02_sforzando.exe
hiq_instruments_sforzando.exe

They all installed to C:\Program Files\PG Music Inc\Band-in-a-Box Sounds

So, do I uninstall these and then install them again explicitly asking it to install to D:?