[quote="conticreative"]Opus uses a number of stand alone applications. Even the preferences look like are a separate .exe.
I wonder if the search pane is also an application called by Opus.[/quote]
Not sure where that idea comes from but it's not the case; the Opus preferences window is part of the same exe, as is the search pane.
The different Opus exes are explained in this FAQ. Almost everything is done by dopus.exe with the other exes only used for a few special purposes.