The way this works has not changed in a long time, especially if we're talking about Opus 10 (there are some differences with how toolbars are saved/restored in Opus 11). If it used to work but no longer does, you must be doing something differently to before.
Everything you should need to set the defaults for how folders are viewed should be in Folder Formats: Quick Guide.
No settings are stored in the registry. If you uninstalled Opus 10 and then re-installed it, you will be using a completely vanilla configuration. (Uninstalling wipes the existing configuration.)
We aren't able to remote into machines, sorry. But I recommend trying the guide again, and making sure to follow each step carefully. It's what everyone else has used, and probably what you used in the past if you got it working before.