1. Start -> Control Panel -> Network Connections -> Local Area Connection (Choose the desired Connection)-> Properties -> Internet Protocol
Click use following ip address link and then type the new ip address. and you should provide the default gateway for it. and you give the dns name for it.
2. You can reconnect the modem give new ip address.
You can not change your IP address without buying some software that can make the address appear to be different than you Ip address, I know you can do it but it may be illegal to do.
In some cases you can simply disconnect your modem for a few hours and it will change. Otherwise you will need to use some type of third-party program.
Go to the system control, choose network connections, select your current connection. Then go to the listbox and choose tcp/ip settings, properties. Now you can thwart the tracking program.
