INT 2F - ZyXEL ZFAX v1.x - INSTALLATION CHECK                                   
	AX = DA00h
Return: AH = enabled state (00h = enabled, 01h = disabled)
	AL = 5Ah installed
Program: ZFAX is the bundled FAX software which comes with the ZyXEL model
	  fax modems.
Note:	This function, and the other DAxxh functions, may apply only to version
	  1 of the software; see AX=DB00h for the version 2 installation check
SeeAlso: AX=CBDCh,AX=DA01h,AX=DA02h,AX=DA03h,AX=DB00h