This is not perfect, but make a group policy with the following options in it, it will prevent most users from installing things:
Computer Config / Admin Templates / Windows Components / Windows Installer / Disable Windows Installer (For non managed apps only)
User Config / Admin Templates / System / Don't run specified Windows applications (setup.exe, install.exe)
(This option only prevents them from being run from a window, such as Explorer or the Run menu, not command prompt or Add/Remove Programs, so:)
User Config / Admin Templates / Control Panel / Add-Remove Programs / Hide "Add a program from CD-Rom or floppy disk" option
And if possible:
User Config / Admin Templates / System / Prevent access to the command prompt
Let us know if this will work for you.
Eric