I can now report an easy solution to one of the reported problems with using the Heritage Muse edition of ESPB: migrating among versions of Adobe Reader. Specifically, we already had a successful installation under Windows XP and Adobe Reader 7, the latter of which we had left installed for the sole purpose of opening the ESPB files. We have now migrated to using ESPB under Adobe Reader 10 on the same computer, and we are deleting Adobe Reader 7.

Among other changes that the ESPB software made when it was first installed under Reader 7.0, it placed three files into a plug_ins folder. (This folder is always present for Adobe Reader, with or without the extra three files.) The exact path to reach this folder seems to vary among different installations, but either "Acrobat 7.0" or "Reader 7.0" is somewhere in the path name. For example, on one computer, this folder is C:\Program Files\Adobe\Reader 7.0\Reader\plug_ins. If all else fails, you should be able to find it by inspecting a shortcut that launches Reader and looking at the subfolders of the folder which contains the executable launched by the shortcut.

These three files have the following names:
FileOpen.api
fOpen32.api
fowp4kbd.api

When we copied those three files to the corresponding plug_ins folder under Reader 10.0, we could open the ESPB files using Reader 10. In addition, the application works better under Reader 10 than under Reader 7. Under Reader 7, we cannot print any of the pages, though we can copy text to the clipboard. Under Reader 10, we can print to our choice of devices and can also copy text to the clipboard.

So, if you simply want to migrate the installation of ESPB to a later version of Adobe Reader on the same computer, it might be unexpectedly simple to do so.

In the process of learning all of this, I also learned a few other things about the fragility of the ESPB installation, about its use of registry keys, and about the possibility of migrating it to another computer altogether. Anyone who's seriously interested in this is welcome to PM me.