Doubtful. Besides, flaws in the messenger SERVICE were exploited not long ago to propagate a virus/worm/trojan. As such, this service was updated and in XP SP2 flipped to the disabled setting.
Why I write doubtful is that Microsoft didn't include any security feature in the "packet" that arrives at the machine. Nothing authenticates it is from machine X, Y or Z. As such, all information in the "packet" can be falsified.
I recently found a small massenger tool which can be used to send net send messages through the network, using a false user name. Are there any ways or softwares (preferably freeware or shareware) to track the actual user name or the IP address of the machine which is used to send these messages(somethin like a packet catcher)?