Is there a way to suppress the dialog box when remotely rebooting a Windows XP machine?[/al_question]
It depends on how you perform the reboot. If you use Remote Desktop to connect to the machine and shut it down via the menu or Task Manager’s shutdown menu I believe there’s no message box. The Windows Shutdown tool presents a message, if I’m not mistaken, when using it remotely. I believe that SysInternals psshutdown will allow you to control whether or not a dialog is shown.