typedef struct _HEADLESS_LOADER_BLOCK
{
     UCHAR UsedBiosSettings;
     UCHAR DataBits;
     UCHAR StopBits;
     UCHAR Parity;
     ULONG BaudRate;
     ULONG PortNumber;
     UCHAR * PortAddress;
     WORD PciDeviceId;
     WORD PciVendorId;
     UCHAR PciBusNumber;
     WORD PciBusSegment;
     UCHAR PciSlotNumber;
     UCHAR PciFunctionNumber;
     ULONG PciFlags;
     GUID SystemGUID;
     UCHAR IsMMIODevice;
     UCHAR TerminalType;
} HEADLESS_LOADER_BLOCK, *PHEADLESS_LOADER_BLOCK;

Windows Vista Kernel Structures