INT 2F U - DOS 3.0+ internal - PERFORM CRITICAL ERROR INTERRUPT                 
	AX = 120Ah
	DS = SS = DOS DS (must be using a DOS internal stack)
	STACK: WORD extended error code
Return: AL = user response (0=ignore, 1=retry, 2=abort, 3=fail)
	CF clear if retry, set otherwise
	STACK unchanged
Notes:	can only be called during a DOS function call, as it uses various
	  fields in the SDAsee Swappable Data Area to set up the registers for the INT 24
	reportedly sets current DPBsee Drive Paramter Block's first root directory sector to 1
SeeAlso: INT 24