Is there a way to stop user to install anything AT ALL. I know that if you have a limited account you can't install...but several programs can install without that privilegies...like...soulseek for example.
There's a program called Fortres 101 which can be setup to restrict many things other than unwanted installations by other users. It's a pretty powerful program. I'm not sure if you want to go that far though. Check it out at www.fortres.com.