Remove "Shutdown" command from w2k PCs but enable restart

We have a Windows 2000 AD environment and want to restrict our PC users 
from shutting off their PCs so we can send out OS/AV patches at night.  
We created a GPO to do this but it also blocks them from restarting.  
 
Many times, issues on PCs are resolved even before the users call the 
helpdesk by rebooting, so we don't want to remove that ability from 
them. 
 
Does anyone know a way that we can remove "Shutdown" while still allow 
"Restart"?
 
I opened a case with MS about this and the rep said that he didn't 
think that it could be done.
 
Thanks,
-Dani
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