Pidgin

If you have used Linux, you Must know about Linux Built-in IM(instant messaging) softwares such as GAIM or Kopete, they are multi-protocole..
for Windows, it's hard to find a Multi-Protocole IM Software,

But Solution is available now...

it's PIDGIN

Pidgin is an IM' program for Windows, Linux, BSD, and other Unixes. You can talk to your friends using AIM, ICQ, Jabber/XMPP, MSN Messenger, Yahoo!, Bonjour, Gadu-Gadu, IRC, Novell GroupWise Messenger, QQ, Lotus Sametime, SILC, SIMPLE, MySpaceIM, and Zephyr.
Pidgin can log in to multiple accounts on multiple IM networks simultaneously.
This means that you can be chatting with friends on AIM, talking to a friend on Yahoo Messenger, and sitting in an IRC channel all at the same time.

you can try it after download it from Pidgin Site
Pidgin runs on all Windows and UNIX platforms. In addition to the source code, they distribute binaries for Windows, Fedora Core, and CentOS / RHEL.