Prevent users software install in RDS

Hello:

I have installed  couple of Windows 2008 R2 RDS in a Windows 2003 Domain, and everything works fine for remote access, the only

item that I cannot figure out is how to prevent users from installing any software on the RDS server other than what is offered.

I have looked at software restriction policy and there has to be an better way to prevent users from installing

any unauthorized software. At the moment users can download anything and run the install so I am not sure what I missing

Any help is appreciated.

Thanks.