Is there a way to send an alert over the network without the use of the Net Send command in XP?

I'm running a scheduled shutdown with the shutdown.exe command, and wish to alert any users on workstation machines that the fileserver is about to perform it's end of day shutdown.

You could send them an email or call them!

For Net Send to work, the Alerter Service needs to be set to Startup Automatically

If the users have Outlook, you could install an Alarm there, at the designated time, to notify them, e.g. Daily at 17:00 Hrs..