IP address is the logical address for verification purposes given to your network card, either dynamic or static, so that you can establish the internet connection and then move ahead with your browsing. This is assigned by the network administrators. If you are a part of the limited network and are connected to the web world through a single address then the outside people will get to know about of your gateway (modem or computer) only.

Now you might want to change the IP address due to the various reasons. It is possible that you are tired of the spam or useless data being sent to you. So the best way is to change it but the service provider might ask you to show the proof of the spam. So have the proof either through screen shots or through history. Another reason could be that your unique address might have been blocked by the administrator from accessing something specific or particular websites. So to evade that ban you might have been thinking about changing your IP.

If your administrator finds it, he might permanently block you. So it is better to seek his permission before doing this. Dial up users and PPPoE users need not worry about it and change as in these cases the IP address is reassigned at the every restart. If you are using cable or DSL modem then you will have permanent IP address. It is better that you call you ISP and ask him to change it. They will give you the guidelines and upon there approval windows users can go to the control panel and then the properties of the local area connection and then TCP/IP and afterward change the your IP. Red Hat Linux users should go to system tools and then to Network and change it.