INT 21 - ENVLOCK - INSTALLATION CHECK                                           
	AX = 6262h
	SI = 1994h
Return: AX = 1994h if installed
	    ES = ENVLOCK's resident segment
Notes:	to deactivate ENVLOCK, zero out the byte at ES:[0102h]
Program: ENVLOCK is a TSR(Terminate and Stay Resident) A program which remains in memory after terminating in order to provide services to other programs or the user.  The name comes from the name of the DOS function call used to remain in memory after termination. by Alexander Yanovsky that forces other TSRs to
	  deallocate their environment when they stay resident