Thanks. The registry settings look correct, assuming Opus is installed in the normal place ( C:\Program Files\GPSoftware\Directory Opus ).
Make sure dopus.exe has not been launched as Administrator, as that would stop non-admin programs from being able to tell it to open folders.
If that also doesn't help, can you describe exactly what is and isn't happening? e.g. Which folder do you double-click, from which program, and what happens when you double-click it?