There are apparently two or more Registry locations controlling Monitoring. Unchecking Options | Monitoring | Enable System Monitoring does not set HKEY_CURRENT_USER\Software\Piriform\CCleaner\Monitoring to zero, but manually using Regedit (or a script) to set that value to zero works as desired: CCleaner closes completely and is no longer running as a background process nor iconized to the taskbar. An entry for HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\CCleaner Monitoring pointing to the CCleaner application also must be manually removed. Note there is also a value for HKEY_CURRENT_USER\Software\Piriform\CCleaner\SystemMonitoring which is set to zero. Caveat Hacker: Registry changes can be dangerous... it is a good idea to back up your PC before making changes.