I realize the thread is old but I finally tracked down the answer, use SuspendState API:

http://msdn2.microsoft.com/en-us/library/aa373201.aspx (Sorry for the VB6 code).

VB Code:
  1. Private Declare Function SetSystemPowerState Lib "kernel32" (ByVal fSuspend As Integer, ByVal fForce As Integer) As Integer
  2. Private Declare Function SetSuspendState Lib "powrprof.dll" (ByVal Hibernate As Boolean, ByVal ForceCritical As Boolean, ByVal DisableWakeEvent As Boolean) As Boolean
  3.  
  4. Public Sub GotoStandbyMode()
  5.     'SetSystemPowerState 1, 0 ' doesn't seem to work...?
  6.     SetSuspendState False, False, False
  7. End Sub