Configure Firefox to change your I.P.

First go to IPLocate.info and check your real IP address.
Then you find a proxy (an new IP address to be shown when you visit web sites).
For example take one from here
After you have chosen the proxy you can start configuring your Firefox 2.x.
Here are the steps:
Open Firefox 2.x
Go to Tools -> Options…
Choose Network tab and press Settings button
In the Connection Settings window, check Manual proxy configuration:
In the same window fill in the HTTP Proxy and the Port taken from the above proxy list (e.g. 216.114.194.19: 6588 where the IP address of the proxy is 216.114.194.19 and the port is 6588) (take a look to the previous picture).
Press Ok and then Ok again and you are done.
After the configuration is completed go to IPLocate.info and check your new IP address. You can now browse anonymously using Firefox 2.x.
Important! After you are done with your activites under hidden ip, do not forget to change your Connection Settings from Manual proxy configurationto Direct connection to the internet.