Remote Desktop Connection

How do I use Remote Desktop Connection? I want to connect between two computers. Both computers are running on Windows XP. When I type in the IP address of the computer I want to connect to, It doesnt work. Someone please explain all the steps to enable this on both computers. THANKS FOR ALL YOUR HELP!

well are the computer on a LAN (Local Area Network) or across the internet?

Re:

This computer is connected through a gateway from our TV service upstairs and the other computer is connected by a wired router sharing two internet connections

well it would be easier if they where on the same LAN

Use this program: http://www.realvnc.com/

Make sure you have the correct ports forwarded on your router also.