From ReactOS

EVENT structure from Windows XP, Vista

typedef struct _EVENTHOOK
{
  THROBJHEAD         head;
  struct _EVENTHOOK *pehNext;
  UINT               eventMin;
  UINT               eventMax;
  UINT               fDestroyed:1;
  UINT               fIgnoreOwnThread:1;
  UINT               fIgnoreOwnProcess:1;
  UINT               fSync:1;
  UINT               fWx86KnownDll:1;
  HANDLE             hEventProcess;
  DWORD              idEventThread;
  ULONG_PTR          offPfn;
  INT                ihmod;
  LPWSTR             pwszModulePath;
} EVENTHOOK, *PEVENTHOOK;

typedef struct _NOTIFY
{
  struct _NOTIFY *pNotifyNext;
  PEVENTHOOK      spEventHook;
  DWORD           event;
  HWND            hwnd;
  LONG            idObject;
  LONG            idChild;
  DWORD           idSenderThread;
  DWORD           dwEventTime;
  DWORD           dwWEFlags;
  PTHREADINFO     ptiReceive;
} NOTIFY, *PNOTIFY;
//
// Notify Flags
#define WEF_SETBYWNDPTI      0x0001
#define WEF_DEFERREDWINEVENT 0x0002
#define WEF_ASYNCHRONOUS     0x0004 // Asynchronous !fSync or Synchronous fSync send
#define WEF_POSTEVENTMSG     0x0008

References

• Windows Symbol files, userkdx.dll, !dso