I do not fully understand. In http://msdn.microsoft.com/en-us/library/aa373163(VS.85).aspx a set of functions is listet. At the bottom some functions listet which are incompatible between XP and Vista. But the function I want to use is "SetThreadExecutionState" which is not listet in this bottom table. The function is described in detail in http://msdn.microsoft.com/en-us/library/aa373208(VS.85).aspx. Because of the bottom of this page, Requirements, I would assume that it should work in W2000, XP, Vista as well as Windows Server 2000-2008. Thanks for your help AthLux