Network terminal device, delivery server and client/server system

A delivery server, comprising:

• a first communication control unit for connecting to a first communication network;
• an OS storage unit for storing an OS downloaded by the first communication control unit;
• an application storage unit for storing an application downloaded by the first communication control unit;
• and
• a second communication control unit for connecting to a second communication network,
• wherein said second communication control unit transmits said stored OS and application to the second communication network in response to a request for the OS and application transmitted via the second communication network.

A client/server system, comprising:

• a first delivery server that has OS data previously stored therein;
• a second delivery server that has application data previously stored therein;
• a third delivery server that receives the OS data from said first delivery server and stores the OS data, activates the OS data as the OS of its own, and receives the application data from said second delivery server and stores the application data;
• and
• a network terminal device that is capable of receiving the OS data and the application data from said third delivery server, activating the OS data as the OS of its own, and activating an application contained in the application data on the OS.