Usually isps give you a static ip so you cannot change your ip address. You can use many programs to spoof your ip, like proxies, von, tor. for surfing the web you can use hidemyass.com
If you want your ip changed without using a proxy (proxies make you lag) then your best bet is to contact your isp and demand to change your ip. They wont do it, but all you have to say is someone keeps hackin you and if the don't change it then you want to cancel your service. That works for me every time. Tech support gets their ass chewed out when ppl cancel their service :p