Windows Control Panel > Network and Sharing Center > Change adapter settings > Right click on the connection to edit and choose Properties > Double click on Internet Protocol Version 4 (TCP/IPv4)
Restarting the computer will renew your IP address. Your IP address is assigned by your ISP / Router what are you trying to do?
You are assuming that no one uses static IP addresses on their local network. Meradz has the correct solution. If you are being assigned an address from a DHCP server, you can open a command prompt (as administrator) and type these commands in:
Are you sure that it is the IP address on your computer that you want to change, not the address on your router? Do you use a router to connect to the internet or just a modem?
I guess the first question is, why do you want to change your IP address?
I recommend you to use Maxidix IP Switcher, i think it is the simpliest and the fastest way to switch IP without restarting, especially if changing of IP goes periodically. Fill IP profile once, and switch it in one click. Here is a link http://www.maxidix.com/products/ip-switcher and here is short video http://www.youtube.com/watch?v=-mu6f7K7Yoc