typedef struct _WHEA_PCIX_BUS_VALIDATION_BITS
{
     ULONG ErrorStatusValid: 1;
     ULONG ErrorTypeValid: 1;
     ULONG BusIdValid: 1;
     ULONG BusAddressValid: 1;
     ULONG BusDataValid: 1;
     ULONG CommandValid: 1;
     ULONG RequestorIdValid: 1;
     ULONG CompleterIdValid: 1;
     ULONG TargetIdValid: 1;
     ULONG Reserved: 55;
} WHEA_PCIX_BUS_VALIDATION_BITS, *PWHEA_PCIX_BUS_VALIDATION_BITS;

Windows Vista Kernel Structures