Is it necessary to keep the software running to maintain the proactive background mode?
No it is not. As mentioned, DiskMagik consists of 2 components. The part which monitors the disk in proactive mode is the DiskMagik Service. The service can be run as a stand alone operation, by enabling it in the program configuration (see Edit menu). It will then run automatically at Windows startup unless it is stopped by the user by using the stop button on main window toolbar. Please note, that even if stopped, when the PC is rebooted, it will be automatically started again at Windows startup unless disabled in the program configuration.