If hibernation has been enabled in the Control Panel -> Power Options applet, you can run the following command to make the computer hibernate.
%windir%\system32\rundll32.exe PowrProf.dll, SetSuspendState
If this works, it should be fairly trivial to make your own shortcut to put into the Start menu to trigger it. Not quite what you're looking for I know.
Is this any help :
How To Put the System into hibernation or Standby from Run menu