To provide a technique preventing unauthorized program installation.

When a user's authentication information is input, a client PC 10 sends the authentication information to a domain controller 20. The domain controller 20 sends an installation control program to the client PC 10 when authenticating the user based on the authentication information. When executing the installation control program, the client PC 10 obtains installation permission definition information from a file server 30 and determines whether or not a predetermined program can be installed using the installation permission definition information. If the determination result is affirmative, the client PC 10 obtains an installer from the file server 30. The client PC 10 executes the installer to install the predetermined program.