LOCK
====
XP (we think, test):
C:\Windows\System32\rundll32.exe user32.dll,LockWorkstation
C:\Windows\System32

Win7:
C:\Windows\System32\rundll32.exe user32.dll,LockWorkStation
C:\Windows\System32



LOGOFF
======
XP (we dunno, test):
??? C:\Windows\System32\rundll32.exe user32.dll,LockWorkstation
C:\Windows\System32

Win7:
C:\Windows\System32\logoff.exe
C:\Windows\System32





=====

Create a new shortcut to:

C:\WINDOWS\RUNDLL32.EXE shell32,SHExitWindowsEx x

Where x is either 0, 1 or 2 based on the following table:

0 - Log off
1 - Shutdown
2 - Restart 