How can i change my Ip address or give a fake Ip ?

Thank you.

You cant change IP address of ISP,
be sure to change ip address and subnet mask of LAN, they are related.
If you need to connect in multiple LAN at same time, go to http://download.cnet.com/IP-Changer/3000-2155_4-10065756.html
but whatever change u made on ur IP, it is local and doesnot affect ISP's gateway IP. That means u cant escape from FBI, if u are using torrent sites, hehe

 Watch this video tutorials 

Follow the below steps for changing IP address in Windows XP:
1.Start->Run->Cmd->Press Enter
2.Type in "ipconfig/release" for Current IP address and
3.Then type "ipconfig/renew" for New IP address .
Or if you want to change your network IP address,
If it is static IP,you cannot change it.Static IP will not change even when you reset the modem.You have to contact your Internet Service provider(ISP) for changing static IP.If your IP address is dynamic,it will change whenever you reset the modem.Before or after changing your IP address,you can check it using Ip-details.com  .

Mpaudel, I am using torrents to download movie. That mean am I going to be screwed ??

 heard of TOR? Your traffic will be anonymous and encrypted. Of course, it'll be a little bit slower but I'll let you be the judge of pros and cons..There is a Firefox plugin for it. Check it out..