There are "dynamic" IP addresses and "static" IP addresses. A dynamic IP address can be changed periodically if you wish to limit tracking that corporations do for pop-up advertising.
In Windows 98 and XP (maybe other OS's also), press the "Windows key" and R (shortcut for START...RUN) and enter IPCONFIG. If you can't find your "Windows key", click on the START menu and click RUN then enter OSK. The brightly colored keys are the "Windows" keys. Now that you know which key is the "Windows key", close the box and use the shortcut so you get used to doing this often in the future to change your IP (you only have to press one of Windows keys).
There are many videos on Youtube that show different ways of changing the IP address (this one shows how to use D.O.S. to change it). The computer I'm using now is 10 yrs. old and has no sound, but the video should show clearly. If you want to see other videos, click twice on the video screen and it will take you to the page on Youtube.
SORRY, clicked on the wrong forum for crossposting.