typedef struct _SYSTEM_POWER_STATE_CONTEXT
{
     union
     {
          ULONG Reserved1: 8;
          ULONG TargetSystemState: 4;
          ULONG EffectiveSystemState: 4;
          ULONG CurrentSystemState: 4;
          ULONG IgnoreHibernationPath: 1;
          ULONG Reserved2: 11;
          ULONG ContextAsUlong;
     };
} SYSTEM_POWER_STATE_CONTEXT, *PSYSTEM_POWER_STATE_CONTEXT;

Windows Vista Kernel Structures