Generally speaking, its hard to get someones IP address from a chatroom. You can 'whois' a user in IRC chat but the host name or IP address you will get is that of their ISP.
To get someones IP you need to have a direct connection from your computer to theirs. When you have a connection established (example: sending a song or image file to someone else) open your MS-DOS window and type netstat -a or netstat -n
This will list all current connections, their host names and IP addresses. Happy hunting.
