From work computer 2, a user makes a reservation in server computer 4 to use work computer 3. The personal verification information and digital signature issued are stored in mobile media 5. This mobile media 5 is then carried and attached to work computer 3. After work computer 3 has completed verification of the user through the personal verification information and digital signature stored in mobile media 5, the same computer environment that was present when that user used work computer 2 is provided.