typedef struct _FLOATING_SAVE_AREA
{
     ULONG ControlWord;
     ULONG StatusWord;
     ULONG TagWord;
     ULONG ErrorOffset;
     ULONG ErrorSelector;
     ULONG DataOffset;
     ULONG DataSelector;
     UCHAR RegisterArea[80];
     ULONG Cr0NpxState;
} FLOATING_SAVE_AREA, *PFLOATING_SAVE_AREA;

Windows Vista Kernel Structures