Editors' Note: Using active surveillance applications may interfere with your system's Antivirus and/or Security protection. Download.com cannot guarantee the security of surveillance software because of their nature.
Family Keylogger - is your best choice, if you want to know what other users on your machine are typing. This heavy weaponry addition to your Spy Arsenal will allow you to know everything! Simply install keystroke logger, set the 'Start in hidden mode' and 'Remove from tasks list' options and you are ready to go. The program will reside in memory while being absolutely invisible for everyone except you.