InitiateShutdown depends on interactive user

[Han Sibot]

I want to automate a weekly reboot of a Windows-XP workstation. I
tried scheduling a reboot application containing InitiateShutdown().
However, it turns out that InitiateShutdown fails sometimes, depending
on the presence of the interactive user. If there is an interactive
user, it works; but if the user has logged out, it fails.

ExitWindows() had the same behavior.
The reboot application always worked on a Windows 2000 server,
independent of an interactive user.

1) Is there another way to reboot, independent of an interactive user?

2) Is this a difference between Windows XP and Windows 2000, or
between workstation and server?