The contents of the Registry related to dviout are all erased by "Option -> Uninstall."
When there is a version upgrade, since the uninstall of the new dviout also acts on the older dviout, the new dviout.exe, dviout.hlp, and dviout.cnt overwrite and are installed. Execute uninstall and then the Install procedure can begin.
Refer to the "Uninstall" item.