typedef enum _KWAIT_REASON
{
         Executive = 0,
         FreePage = 1,
         PageIn = 2,
         PoolAllocation = 3,
         DelayExecution = 4,
         Suspended = 5,
         UserRequest = 6,
         WrExecutive = 7,
         WrFreePage = 8,
         WrPageIn = 9,
         WrPoolAllocation = 10,
         WrDelayExecution = 11,
         WrSuspended = 12,
         WrUserRequest = 13,
         WrEventPair = 14,
         WrQueue = 15,
         WrLpcReceive = 16,
         WrLpcReply = 17,
         WrVirtualMemory = 18,
         WrPageOut = 19,
         WrRendezvous = 20,
         Spare2 = 21,
         Spare3 = 22,
         Spare4 = 23,
         Spare5 = 24,
         WrCalloutStack = 25,
         WrKernel = 26,
         WrResource = 27,
         WrPushLock = 28,
         WrMutex = 29,
         WrQuantumEnd = 30,
         WrDispatchInt = 31,
         WrPreempted = 32,
         WrYieldExecution = 33,
         WrFastMutex = 34,
         WrGuardedMutex = 35,
         WrRundown = 36,
         MaximumWaitReason = 37
} KWAIT_REASON;

Windows Vista Kernel Structures