gnome/kde and hiding "power off" menü

[Boris Glawe]

Hi,

is there a way in kde or gnome to hide the buttons, which gives the user 
controll over the machine's power state (power off, reboot).

I've found this feature in the gdm.conf, where I can set a variable 
called "SystemMenu" to "false". But the user can still power off the 
machine after having logged in into either kde or gnome.

thanks for any hint

greets Boris