Format of Card Services Client Registration record:
Offset	Size	Description	)
 00h	WORD	attributes
 02h	WORD	event mask
 04h	WORD	client data (passed to client event handler in DI)
--- 16-bit code ---
 06h	WORD	client data selector (passed to event handler in DS)
 08h	WORD	client data offset (passed to event handler in SI)
 0Ah	WORD	reserved
--- 32-bit code ---
 06h	WORD	reserved
 08h	DWORD	client data offset (passed to event handler in ESI)
------
 0Ch	WORD	expected Card Services version (0210h for v2.10)