We recommend that you set Opus to start automatically when Windows starts, using the options in the Launching Opus / Startup page in Preferences. Opus is designed to stay running in the background, even when no windows are open. There are several advantages to this:
You can also treat Opus like a traditional file manager, that you run when you need it and exit when not using it. The installer can place shortcut icons on the desktop and in the start menu, and you can use these icons to run Opus. You can also pin the icon to the taskbar and launch it that way.
To quit Opus when you're done using it, select the Exit Directory Opus command from the File menu in a Lister, or right-click on the taskbar notification icon (if enabled) and choose the exit command from that menu.
You can also set Opus to exit automatically when the last Lister is closed, with the Shutdown Directory Opus when all functions finish option on the File Operations / Options Preferences page. With this option on, and Opus not set to run on startup, it will behave like a traditional, monolithic file manager.
We don't recommend killing the Opus process via task manager - you may end up with configuration files not saved or corrupted.