2 types of IP addresses:
1) Static. this is a never changing IP assigned by your ISP only to you. I would be very suprised if you have a static IP. the only way to change it is to call your ISP and ask them to change it.
2) Dynamic. This means that you are randomly assigned an ip by your ISP each time you log on. To change this(assuming you are using windows xp), open up your control panel, go to network connections, Right click on your local area connection and choose "repair" this will release your old IP and grab a new one. You may or may not have the same one reassigned.
Jim R
June 2008