okay, if someone lived in wales and logged on using an IP hider and someone in ireland did the same, would there be any chance of them ever having the same IP?
If by IP hider, you mean proxs server then yes, they would both be shown as having the proxy server's ip. This is usually used by people who don't want their surfing traced back to themselves.
There is no possibility to have 2 separate IP addresses as same. Even if you set same IP address in a LAN, an IP conflict error message will occur. To get your Local IP address, goto start->run->cmd->ipconfig/all which will show the computer and subnet mask IP address.To check your External IP address, visit the site http://www.ip-details.com .