How can a public IP address be changed to a private IP address?

I believe the question is irrelavant. First, let's start off by explaining what is an IP. IP is short for 'internet Protocol'. So the IP address is used to identify machines to each others at the 'network' layer in OSI layer terms. Machines connected to each others form a LAN or a WAN. It's the connection between thousands of machines which creates the internet. a machine may be connected to a LAN that is not connected to the internet backbone. This makes the machine private. However, as this machine wants to access machines on the internet backbone, a protocol called NAT (Network Address Translation) is implemented on an intermediate machine itself connected to the internet, and would impersonate the original machine in its requests and its response, playing effectively the role of a gateway. With that said, a public ip identifies a machine connected to the internet backbone. If this machine is connected to other machines, it may identify itself through the LAN created between them, This identification may use a public ip or a private IP. If the purpose of the user is to no longer have this machine visible to the internet backbone, he would simply assign a private IP to it, in a way its peers can relay traffic to it by being on the same network, or route traffic to it through an intermediate router. For more info on my work, jump to http://publicip.info