If the above does not result in your IP address changing, please look through the below for the situation that best matches yours and attempt to change your IP address that way. Unfortunately you are not able to get your IP address to change in all cases, as it is ultimate determined by your ISP's DHCP configuration (when you've got a dynamically assigned IP address, that is.)
Windows - Computer connected directly to the modem
Get to a command prompt. (START, run, cmd).
Type "ipconfig /release" (without the quotes, on the command line by itself).
Type "ipconfig /renew" (without the quotes, on the command line by itself).
Windows (second option) - Computer connected directly to the modem
Get to a command prompt. (START, run, cmd).
Type "ipconfig /release" (without the quotes).
Shut down computer.
Turn off computer.
Turn off all ethernet hubs/switches.
Turn off cable/DSL modem.
Leave off overnight.
Turn everything back on.
GOOD LUCK !!!