Teenagers can be stopped from playing computer games by unplugging the computer or video game console. Parents can engage their teens in other activities other than Video Games to curtail computer game playing as well.
It depends on the circumstances.
Preventing them from being installed in the first place is one approach; this can work in settings where users only need to do very specific tasks (one example might be a computer in a public library which is intended only to allow users to look up library holdings in a computerized card catalog). The users are given just enough permission to do those particular tasks, and are specifically forbidden from installing other programs.
It's also possible to set up a computer so that it "resets" itself to some base state if by some chance it is changed. This doesn't necessarily prevent users from installing games, but it does mean that they have to reinstall the game every time they sit down at the computer, and can't "hide" it away somewhere for future use. This makes playing games enough of a hassle to limit them even if it can't eliminate them entirely.
Finally, in situations where the users may occasionally need administrative privileges and also need to be able to retain their changes over long periods of time (an office environment, for example), they can always be required to sign an agreement stating that they will not install games and that their computer use may be monitored (either physically or electronically, using remote monitoring software) for compliance.
Get him a PS3 with an internet connection
Only one thing teen boys think about more than video games: girls. If you can't force or convince him to stop playing, tell him girls won't find him interesting and that he should do some sport or read a book. Alternatively, you could turn it into a positive experience: he could write about the games he plays or keep a blog.
wAIT
The duration of American Teen is 1.58 hours.
The duration of Teen Witch is 1.5 hours.
The duration of Teen Kanya is 1.87 hours.
The duration of Teen Wolf is 1.52 hours.
8 to 10 hours
As long as they have probable cause they can stop you for anything they want.
The max amount of hours a teen should play is about 5 hours. Anything more could have some effect on the brain.
The duration of Teen-Age Strangler is 1.02 hours.
The duration of Not Another Teen Movie is 1.48 hours.
The duration of Teen Wolf Too is 1.57 hours.
The duration of Teen Choice Awards is 2 hours.