Instead of Using MiRC that almost been world wide well know, we personally suggest you (Recommended) to use this Free (Open Source with GNU License) IRC Client for your Operating System, including UNIX System such as MacOSX, Ubuntu, and others, and also you Windows in Win32 such as XP, Vista or 7, called KVIrc. Though it seem not easy to install because you need to compile the source code and others process you you have to do, this IRC Chat Client has many great features.
Features in KVIrc
There plenty of Features available in KVIrc. Some of them you can read as follows: In user Interface you can get, Full GUI Based Configuration, Floatable Windows (MDI), Hepl, Themes, Emoticon, Editing ToolBar, Status Bar, Notifier Pop up, and support 14 Languages Translation; Networks you can had IPv6 Supported, Proxy with SOCKSv4 or v5 and also HTTP, SLL Support; For IRC features you can use Multiserver Connection, Notify List, Ignore List, Lag Metter and many more.