When you changed the password, you made it impossible for any prrogram to use the same trick to message your contacts, I think, and also impossible to send messages from that account under your name.

I also think that the people who used the trick have no way of knowing who the trick worked on, the only way they know it worked on anyone is because the volume of messages at the 'lose weight now!' or whatever site goes up. They just sent a bunch of messages at Hotmail and caught some victims.