Miranda IM is an open-source multi protocol instant messenger client for Microsoft Windows. It's smaller, faster, easier!
Miranda IM is a multi-protocol instant messaging client for Windows. Very light on system resources and extremely fast, Miranda IM requires no installation and can be made to fit on a single floppy disk or USB drive. Featuring a powerful plugin-based framework and boasting over 350 plugins, Miranda IM is one of the most flexible and customisable messaging clients on the planet. To see how some of our users have customised Miranda IM, check out the screenshot section.

Protocol Support
* AIM (AOL Instant Messenger)
* Gadu-Gadu
* IAX (Inter-Asterisk Exchange)
* ICQ
* IRC (Internet Relay Chat)
* Jabber
* MSN
* Netsend
* Tlen
* Yahoo
* And more...

Supported Operating Systems
* Windows 95 / 98 / ME / NT / 2000 / 2003 / XP / Vista

Homepage - http://www.miranda-im.org/