Ip Adresses

Makes a difference to what? What are you trying to accomplish?

DSL: it changes every once in a while.

Cable: you can try calling your ISP (Rogers, Cogeco, etc) and requesting that you be assigned a different I.P. I'm not sure if it is possible.
 
in Windows open the console or terminal thingy or whatever it is called: ipconfig /release
then type ipconfig /renew should work.
On a Mac open system prefs open network then hit "renew lease".
The windows one worse but i might be wrong on the syntex as i never use windows.