New versions of MuseScore should change default app for MS files
When I upgraded from version 1.x to 2.0.3, MuseScore left the default application for MS files to open with 1.x. Any new version of an application should automatically update the default applications for its files to the new version, even if the old version stays on the computer as is the case with MS 1.x vs MS 2.0.3.
I manually adjusted this so it is not an issue on my computer today, but users should not need to do that. I don't remember what version of windows I was in when I upgraded. I currently use 10, but I think I upgraded MS before Windows.