typedef enum _INTERFACE_TYPE
{
         InterfaceTypeUndefined = -1,
         Internal = 0,
         Isa = 1,
         Eisa = 2,
         MicroChannel = 3,
         TurboChannel = 4,
         PCIBus = 5,
         VMEBus = 6,
         NuBus = 7,
         PCMCIABus = 8,
         CBus = 9,
         MPIBus = 10,
         MPSABus = 11,
         ProcessorInternal = 12,
         InternalPowerBus = 13,
         PNPISABus = 14,
         PNPBus = 15,
         MaximumInterfaceType = 16
} INTERFACE_TYPE;

Windows Vista Kernel Structures