Here is a beautiful tips to change your IP adress if you are banned in forums, websites or IRC chat rooms..
The ip address assigned to your PC is linked to the mac address of the device that is connected. A USB connection will always have a mac address one digit higher than the mac address of the cable modem, whereas an ethernet connection uses a NIC which has it’s own mac address. An ip addreess can be forced to change by changing the mac address of a device in one of the following ways:

• switch from usb to ethernet or vice versa
• change network cards
• change the mac address of the NIC

Changing a NIC’s mac address

Windows
Go into device manager and then the properties of the network card. In the “advanced” section there is an option to change the network address/ physical address/ mac address. Check the current mac address using ipconfig /all from a command prompt and then increase the mac address by one digit. Reboot everything and you should have a new ip.

Apple Mac
NB- this procedure will only work on a mac with terminal- ie os 10.1 or higher

Open a terminal window and type:

sudo ifconfig en0 ether 00:00:00:00:00:00

where en0 is the interface you are using, and the zeros are the mac address that you want to use.

Linux
When logged in as root type:

/etc/init.d/networking stop
ifconfig eth0 hw ether 00:00:00:00:00:00
/etc/init.d/networking start

Notes

Leaving the connection off for a period of time does not guarantee the same ip address, because even if the lease has expired, if the ip address has not been assigned to someone else you will get the same ip back again. Also reinstalling the ntl software will not give a different ip unless you use a different device to connect.