Automatically Kill Programs At Shutdown:

don't you hate it when, while trying to shut down, you get message boxes telling you that a program is still running? Making it so that Windows automatically kills applications running is a snap. Simply navigate to the HKEY_CURRENT_USERControl PanelDesktop directory in the Registry, then alter the key AutoEndTasks to the value 1.

No Shutdown:
Wanna play with your friends by removing the shutdown option from start menu in their computer.
Try This!!!
Regedit
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer
"NoClose"="DWORD:1"

Display legal notice on startup:
Wanna tell your friends about the do's and dont's in your computer when they login in your absence. Well you can do it pretty easily by displaying a legal notice at system start up.
REGEDIT
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system]
"legalnoticecaption"="enter your notice caption"
"legalnoticetext"="enter your legal notice text"