hmm....when you say that you mount the boot.iso in its' place, did you also load the Lamento_DVD.iso on the 2nd device that is supposed to be set on Daemon tools....if both are not loaded together, i don't think the game can work...other than that i'm not very sure why is it not working....
do check that your computer has been set to Japanese system before install the game....if not it will not work too....