Tried this?
http://support.microsoft.com/kb/927847

pretty much impossible without unplugging the router's wan port imo

even if you cna block all the ports, it tunnels through http, and if you can stop that, the users will just use a webbased client, so you'll have to block all of them too

uninstall?

windows policy and disallow it from being run

Yeah it's a complete bitch

What I have done before is just fucked with the permissions of the .exe

But as mentioned there's still meebo etc

Just out of interest, why would you block it?

request from friend to stop daughter from using it (grounded or something). Computer nub so i doubt she would use meebo and the like. Thought i could just admin the router remotely but it looks like i'll have to go over there and just break the msn proxy settings or something. Im lazy but that would probably be easier than trying to fight it off from the router. Thanks for the inputs

Cheers

Don't forget to block http://webmessenger.live.com or http://webmessenger.msn.com

Whichever it is...

yep we used msn internally at my last job, its easier to talk to everyone where ever they are, at home, onsite etc, and you can send files links etc.

Also, yeah pretty hard to block MSN, it uses internet explorer proxy settings so you might break IE if you change the proxy settings.

Yeah well make sure you block meebo too!