Info: Which ports does IM use

[chicagotech]

Q: Helllo, I have a small netowrk (10 server, & 60 desktops) that I want
to block IM completely thoughout the network.

What is the easist, least expensive way to block IM that is centralized
(not needing to install something on each PC.

I have turned off the specific IM ports, so I am assuming IM is using
port 80 for access inside my network. I cannot turn off port 80.

Thanks for any help
Gerald

A: Instant Messaging Ports
AOL port 5190
ICQ port 4000
IRC port 6667
MSN port 569 or 1863
Yahoo port 5050