We can't actually check your PM's, you will have to screen shot them and post them here.
I need to see:
A post or PM where he says his MSN address (matching the one in the pics above)
Some background information about the trade
Pictures of you trading the RSN he states in game and giving over the RSGP, or a picture of you sending money to his PayPal (whatever you were trading for the account)
Any of the PM's you exchanged that would be helpful in proving his guilt