I've never tried sniffing MSN conversations, so someone else might have more specifics. However, if the conversations are, in an way, encrypted, you'd need to have the proper certs, etc, to be able to decrypt the conversation. If they are NOT, the simply selecting one of the packets from the conversation, and right-clicking on it, you can choose 'Follow TCP Stream', and that'll separate out the conversation packets, and open a window of the decoded conversation between the two machines.
So, to clarify, if encrypted, prolly not. If not, follow the stream, and see what you get.
~ hayabusa ~
"All men can see these tactics whereby I conquer, but what none can see is the strategy out of which victory is evolved." - Sun Tzu, 'The Art of War'
OSCE, OSCP , GPEN, C|EH