Function 17h	Set Disk Type for Format (diskette)	     (except PC and XT)
entry   AH      17h 
	AL      00h     no disk 
		01h     360kb diskette in 360Kb drive 
		02h     360kb diskette in 1.2M drive 
		03h     1.2M diskette in 1.2M drive 
		04h     720kb diskette in 720Kb drive 
	DL      drive number 
return	AH	status (see Int\13f\01)
note    This function is probably enhanced for the PS/2 series to detect 
	1.44 in 1.44 and 720k in 1.44.