typedef enum _HEAP_FAILURE_TYPE
{
         heap_failure_internal = 0,
         heap_failure_unknown = 1,
         heap_failure_generic = 2,
         heap_failure_entry_corruption = 3,
         heap_failure_multiple_entries_corruption = 4,
         heap_failure_virtual_block_corruption = 5,
         heap_failure_buffer_overrun = 6,
         heap_failure_buffer_underrun = 7,
         heap_failure_block_not_busy = 8,
         heap_failure_invalid_argument = 9,
         heap_failure_usage_after_free = 10,
         heap_failure_cross_heap_operation = 11,
         heap_failure_freelists_corruption = 12,
         heap_failure_listentry_corruption = 13
} HEAP_FAILURE_TYPE;

Windows Vista Kernel Structures