Display a Messagebox

Hello,
I'd like to display a messagebox when my computer logon screen is displayed.

Thanks

By the way, I would like to do this in Vista

I thnik you need to write a service. That's one of the few things that will be loaded before the user logs on. What's the messagebox for ?

Are you talking about the messagebox displayed at the logon screen saying "Legal caption notice". If yes then its a simple registry tricks. Just follow this