Mishomi,
With Platina, what message did you get? The one about disc 2? It's normal since it'll need disc 2 in order to finish off the installation.
As for Alex...
Did that message pop up when you actually mounted disc 1? You might have mounted disc 2 instead; that's why the computer is asking for disc 1 (disc 1 is actually the installation disc whereas disc 2 is the game/playing disc).
Again these are just my speculations. I'll be able to understand your problem more if I can get some Japanese-text boxes (instead of the gibberish-text) on your screenshots. ^^;