To remove Windows NT / Windows 2000's ShutDown button from the Start Menu, apply the following registry hack :

Hive: HKEY_CURRENT_USER
Key: Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Name: NoClose
Type: REG_DWORD
Value: 1

To prevent Logoffs in a kiosk evironment:

Hive: HKEY_CURRENT_USER
Key: Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Name: NoLogoff
Type: REG_DWORD
Value: 1

Desktop and Explorer Restrictions Tips:

Desktop icons hidden
File menu in Explorer is removed
Map Network Drive and Disconnect Network Drive menu from Explorer removed
Network Neighborhood icon removed and prevent network access from Explorer
Common Groups from Start Menu removed
Find command removed from Start Menu
Run command removed from Start Menu
Shut Down button removed from Start Menu
Control Panel, Printers and My Computer in Explorer hidden and on Start Menu
Taskbar on the Start Menu hidden
Most Recently Used entries removed from Run history
Menus do not display upon right click on Taskbar, Start Button, Clock, or Taskbar icons
Menus do not display upon right-click of Desktop or Explorer's Results pane.
Only programs in Restrict subkey can be run
Remove Run command from Start menu

Gives an in-depth look at the NT/Windows 95/98 system policies. Step-by-step walkthroughs.

title says it all