If you are a worried parent or employer who is constantly thinking how your computer is being used, you could use employee or kid monitoring software.
One such software is SniperSpy which allows you to remotely watch your computer like a television. The software also saves screenshots along with text logs of chats, websites, keystrokes in any language and more. You can remotely view everything your child, employee or anyone does while they use your PC.
The beauty is that you can install the software remotely through a simple e-mail. You can even issue a command that allows you to shutdown a PC, logoff a user or freeze a mouse.