Square Enix seems to be treating them like separate games at times, but also calls them just fixing the old one. I can't find any conclusive evidence on this. What do I need to do to play?
Update:
I try logging into the website to download the client, and it says I need to sign in to the game first. I can't sign in to the game until I have the client installed, but my disks are for the old client. Where do I go from here?