Internal instant messanger..

All, In company that i work, some of my friends and me using Yahoo Messanger as instant messanger, right now I think to switch to anohter instant messanger that only run Internaly. So right now, I'd like to know what instant messanger that can run in window$ and hopefully in Linux. I see that windows communicator is almost good for my purpose, but they dont have any linux version. regards, -- Arie Reynaldi Zanahar reymanx at gmail.com http://www.reynaldi.or.id