typedef struct _ETIMER
{
     KTIMER KeTimer;
     KAPC TimerApc;
     KDPC TimerDpc;
     LIST_ENTRY ActiveTimerListEntry;
     ULONG Lock;
     LONG Period;
     UCHAR ApcAssociated;
     UCHAR WakeTimer;
     LIST_ENTRY WakeTimerListEntry;
} ETIMER, *PETIMER;

Windows Vista Kernel Structures