mIRC

mIRC:

What is IRC?
Based on the chatting client, this is a good explanation on how to get started, easily.

mIRC 6.3 has been released!

This version of mIRC offers full Vista compatability with support for limited user accounts, U3 support, support for tips (those small text balloons that pop up near the Windows tray) to notify you of various events such as incoming messages or users in your notify list coming on or leaving IRC, support for positioning the Treebar at top/bottom of the mIRC window, and a feature that allows you to switch between Normal and Compact modes. Compact mode makes mIRC behave like a messenger with the treebar filling the main window, all windows opening on the desktop, and so on.

http://www.mirc.co.uk/get.html
http://www.mirc.com/