When I first set Opus up, I set it to be the default over windows explorer. This worked the first time I opened a file shortcut but since then only windows explorer opens. I tried looking in the "Settings" "Preferences" for the category "Launching Opus" so I could check it was set to start at start-up and be the default. However I don't have that category available. In fact I only have 10 of the 16 categories that should be available in "Preference" (according to the help guide).
Any ideas?