typedef enum _MI_VAD_TYPE
{
         VadNone = 0,
         VadDevicePhysicalMemory = 1,
         VadImageMap = 2,
         VadAwe = 3,
         VadWriteWatch = 4,
         VadLargePages = 5,
         VadRotatePhysical = 6,
         VadLargePageSection = 7
} MI_VAD_TYPE;

Windows Vista Kernel Structures