I have had a problem for a few years that when I vpn into a client's network, Windows Messenger automatically starts up and signs me in. Without even showing me anything in the systray. It's a little frustrating only because if I am VPNing in, that means I'm working and don't have time to chat.

I finally googled the problem today and discovered that there is a somewhat hidden setting in Windows XP which allows you to stop Windows Messenger from starting up on it's own. Here is the MSDN Support article on it.