I am starting a sticky thread and am in the mix of writing up a how-to guide for every type of connection, what type of connection do you have? what service do you have? Do you have access to the router settings? What type of operating system are you running, ie; windows, mac, android, unix,solaris? do you need to change you IP or your mac or both?
My other method is using a software called VMware and it allows you to run multiple operating systems on your main CPU i suggest you have atleast 1GB of ram, I have 32GB of G-Skill and a i5 sandy unclocked quad core running with windows 7 and 5TB's of space running the vmware on my SSD which is a faster hard drive then your basic hard drive. enough about my cpu, you can install vmware and use any operating system you wish, if you are familiar with linux it is a lot easier to spoof your ip and mac via linux but it can also be done with windows. I prefer using vmware because were able to have multiple systems running and operating multiple accounts without having to change router settings, etc... but for now if you want do this;
1. go to start and type "cmd" where you would to search for files
2. once prompted with the command prompt type in "ipconfig /release"
3. unplug your connection to the internet and shutdown your cpu, you MUST shut down and not reboot.
4. UNPLUG the power source for your router, you must unplug it and not just power it off with the on/off toggle. IF YOU CAN UNPLUG THE SOURCE OF THE INTNERT, IT USUALLY IS LOCATED OUTSIDE OR INSIDE YOUR HOUSE WITHIN A BOX AND USUALLY CONTROLS ALL YOUR CABLE BOXES OR PHONE SYSTEMS BUT TRY AND DO THIS AS I FOUND THIS MOST EFFECTIVE.
5. power back on your cpu
6. type in "cmd" again and repeat step 2
7. type "ipconfig /renew" in the command prompt
8. plug back the internet connection and plug the router back on.
9. repeat step 2 again
10. repeat step 7 again
now check your ip it should have changed, if this does not work you need to follow steps 1-4 and do not touch anything for 2-4 hours (MAKE SURE THE SOURCE OF THE INTERNET) IS ALSO UNPLUGGED FOR THE DURATION) depending on your lease with your provider. that should change your ip guaranteed, if it does not which i highly doubt PM me, make sure to take down your current ip address and mac address prior to doing this method. You can use ipbuger(dot)com to check your ip and to check your mac address type "ipconfig /all" in the command prompt, if you do all that work and don't remember your old information you will be pissed trust me I've forgot before.
I still suggest using VMware but until i finish my howto try those methods.