Determine whether Windows is shutting down or restarting?

I have a backup program that runs automatically as a shutdown script on Windows 2000 and XP computers. I'm trying to add some code that will cause the backup to be skipped if the computer is restarting instead of shutting down.

Is there anyway to determine whether Windows is performing a restart or shutting down? I don't care how it works as long as it works.

Thanks!