A few upgrades back (I forget exactly which) we changed the installer for Congo upgrades.
Before the change, the registry keys that Windows XP Embedded uses to populate that list were left alone, with an extra entry being added for the newest version so you could see a list of previously-installed versions.
Now we've made that change, the installer isn't adding an extra key but instead changes the previous one to indicate the currently-installed version only.
You can safely ignore this list, and you don't need to open it when doing an upgrade 'manually', as you only need to open the memory stick and run the installer program.
In Congo 5.0 we are revamping the system settings dialog and the upgrade process again to make it much more friendly.
www.etcconnect.com