INT 7F - TIGA Communications Driver v2.05 - INSTALLATION CHECK                  
	AX = 4321h
Return: AX = 0000h if installed
Note:	INT 7F is the default, but may be overridden
SeeAlso: AH=01h"TIGA",AX=1234h,AX=2525h,AX=4321h,AX=5555h