The password you need to provide for installation is your Mac admin password, it has nothing to do with your XDK password. This is an unfortunate side-effect of the way the installer presents that password request.
The password you need to provide at this point in the installation is the same you would provide if you saw one of these dialogs:
I have tried the Mac Adamin pass (the password which will be asked when installing new apps), but it seems to be the wrong ...
I will try to delete all preferences from the older version