If you don't want the installation monitor to automatically detect program installs, just right click on the installation monitor's system tray icon, and uncheck the Automatically monitor installations item from the menu that appears:
If automatic install detection is disabled you can enable it by checking the menu item above.
Please note that if the installation monitor is not running in your system tray, the installation monitor can not detect new installations, simply because it isn't running. You can, however, manually start monitoring a program's installation if you start the installation monitor first.