Your able to change your IP a number of ways, but ultimately it all depends on how your ISP is configured.

Certain routers allow you to refresh IP settings by going into the control panel normally accessed via http://ipadress you can then choose to renew IP addresses. Normally you'd then have to wait overnight for that to take effect.

Another way is to go into command prompt > start > programs > accessories > command prompt (or type cmd in search).

When the command line loads type:

ipconfig /release

then

ipconfig /renew

Like I said, ultimately wether it works or not is down to how your ISP allocates IP addresses.

Hope that helps in some way anyway.

Tim