INT 21 - DOS 1+ - DISK RESET                                                    
	AH = 0Dh
Return: (DOS 6 only) CF clear (earlier versions preserve CF)
Notes:	This function writes all modified disk buffers to disk, but does not
	  update the directory information (that is only done when files are
	  closed or a SYNC call is issued)
SeeAlso: AX=5D01h,AX=710Dh,INT 13/AH=00h,INT 2F/AX=1120h