For what it's worth, I went to the Registry Editor, deleted the entries in HKEY_CLASSES_ROOT for Skype and Spotify completely, and these are still showing up as installed.

Makes me wonder if Windows is somehow pre-installing custom scheme handlers for these, whether you have them or not. As far as I know, Skype comes with Windows, so there is no way to test a fresh installation that never had it at all, but Spotify? Is there anyone using a completely clean fresh Windows installation that can test if this demo thinks it is installed even though it isn't?