I use this at every client I've ever serviced (I'd have to review my notes on the Windows 98 side of the equation) and it works flawlessly for every 2000/XP client I've come across.
Here's the cliff notes:
Add Scheduled Action Policy (for a workstation policy) called Poweroff
Working Directory: \\srv\sys\public\tools\
Parameters poweroff -force -warn -warntime 600 -msg "Computer will shutdown in 10 minutes. CLICK CANCEL TO STOP AUTOMATIC SHUTDOWN!!"
Priority Above Normal
Policy Schedule Tab
Runs every day of the week from 5 pm to 11:50 pm
Retries every 30 minutes
Advanced | Completion
Advanced | Fault
Retry every minute
Advanced | Impersonation
Advanced | Priority
Advanced | Time Limit
This works out great for my clients and everything is done on the server and nothing really takes place that makes you do local workstation changes. So...that's pretty nice in my opinion.
It's worth a try ;)