I dug around and did find a downloadable executable of Proview 2.1 on archive.org and it installs and runs. Unfortunately, it seems that the only files that it can edit are "working" files. The final executable versions that it spits out as standalone players don't seem to be openable.

I even set all the type, creator, and other attributes of my file to match that of a new standalone player produced by PV and my file still didn't run.

I'm waiting for my friend to send me the original version of the file on a floppy. There must have been something lost during the process of electronically sending me the file.