If you're speaking of IRC, there's a ton of different clients. Since your on Windows your best bet would be mIRC. http://mirc.com
If you happen to be on Linux (which I highly doubt), your best choices are XChat, or Irssi -- http://xchat.org , http://irssi.org
mIRC is a program that connects to IRC networks - IRC was started way before instant messengers. IRC is in a chat room (but their called channels, and they were around a long time before the chat rooms that you see on sites).
Trillian is a program that allows you to connect to multiple diffrent IM networks AND IRC networks.