An IP address is a unique string of numbers that identifies a computer or server on the Internet. This address can be used for special functions, such as remotely accessing your computer.
Open Command Prompt. In Windows XP, click Start, then All Programs, from here go into "Accessories" and click "Command Prompt". You can also open it by clicking Start, then click Run, then type command and click OK.
Notice there will be a black box. Type in ipconfig.
Wait and you will be given your IP address, DNS address and possibly some more information.
Alternate Method
Follow this link: http://myipaddress.com/show-my-ip-address/
Tips :
Beware that this only works if you aren't on a local network. Otherwise it will be giving your local and not you main one that expressed on the Internet. If your IP Address begins with "192.168", then you are reading your local IP address.
You can quickly access your IP address by visiting websites such as the ones listed below under "Sources and Citations"...
Your IP address is set in this form: xxx.xxx.xxx.xxx.
Your IP address can only contain numbers (in place of the xxx) from 0 up to 255, so lets say you go on a site claiming to show your IP, and you get an IP address saying 0.288.288.274, it wouldn't be a real IP, but it could be 207.184.24.254.
Warnings :
If you are on a LAN, you will get the LAN IP with the above steps.
When using an IP information site from a service that uses a web proxy (such as AOL), be aware that the reported IP may be that of the service's web proxy and not your actual IP.
Don't download any software claiming to show you your IP.
Source : http://www.wikihow.com
