Hide the "Add programs from your network" option
User Configuration\Administrative Templates\Control Panel\Add/Remove Programs
Prevents users from viewing or installing published programs.
This policy removes the Add programs from your network section from the Add New Programs page. The Add programs from your network section lists published programs and provides an easy way to install them.
Published programs are those that the system administrator has explicitly made available to the user with a tool such as Windows Installer. Typically, system administrators publish programs to notify users that the programs are available, to recommend their use, or to enable users to install them without having to search for installation files.
If you enable this policy, users cannot tell which programs have been published by the system administrator, and they cannot use Add/Remove Programs to install published programs. However, they can still install programs by using other methods, and they can view and install assigned (partially installed) programs that are offered on the desktop or on the Start menu.
If you disable this policy or do not configure it, Add programs from your network is available to all users.
If the Hide Add New Programs page policy is enabled, this policy is ignored.