The description of LUPC: Set time limits on Windows, games - Play With New Friends
LUPC is an easy-to-implement, user-friendly piece of software designed to help you monitor and limit user time on your home computers. LUPC can limit user time on windows session or internet connection or programs (applications): Games, Internet, Seafight, Counter-Strike, Merlin... Once you have set up all the users accessing the computers in your home, you can then set maximum daily or weekly time limits for each person and you can easily specify which days of the week and hours of the day there are allowed access. Once the user's time is up they will be warned and the automatically logged off.
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