INT 21,69 - Get/Set Disk Serial Number (Undocumented DOS 4+)

	AH = 69h
	AL = 00 get serial number
	   = 01 set serial number
	BL = drive (0 = default, 1=A:, 2 = B:, ... )
	DS:DX = buffer to contain extended BIOS Parameter Block (BPB, AL=0)
	      = disk information to set of the form:

	  Offset  Size		Description
	    00	  word	  info level (zero)
	    02	  dword   disk serial number (binary)
	    06	11bytes   volume label or "NO NAME    " if not present
	    11	 8bytes   filesystem type string "FAT12   " or "FAT16	"

	returns:
	CF = set on error
	   AX = error code if CF set
	      = 01  network drive not supported
	      = 05  no extended BPB found on disk
	CF = clear if successful and value in AX is destroyed
	   AL = 00  buffer filled from Extended BPB on disk
	      = 01  disk Extended BPB updated from buffer
	DS:DX = pointer to returned data, when AL = 0


	- copies data from Extended BIOS Parameter Block to buffer
	- no critical error is generated on error
	- does not work on network drives (returns 01)
	- returned buffer (after offset 2) is similar to offsets 27 through
	  3D of the Extended BPB found in the boot record

	- see  INT 21,59