I think one problem might be that I'm using 64-bit WIN10 (successfully with Finale 2009) and trying to load 32-bit Dolet 7, It's a non-starter. For the moment, thanks to Michel and other who tried...
Thanks, Michel, I haven't checked for versions of MusicXML - but it's a good point - as I simply use files found on cpdl.org, which is a vast repository for (mostly) choral music, but I don't reall...
Many thanks for replying, even if it was all lost in the process! Perhaps there's a nugget you can offer that might help me get on the right track Adrian?