I just tried that fix, it sadly did not work. On reflection it would have been simpler to ask the player to uninstall the old 32 bit version of the game, reinstall using the 64 bit version (download the launcher.exe from the web site). It could then be installed in C:/Program Files. I am hoping that they can patch the launcher process as whilst my client is installed, when I hit play nothing happens.
I even tried run program in compatibility mode for Windows 8