Which gave me “The address wasn’t understood” from Firefox. Took a while as most spotty users aren’t exactly Linux hackers. It took me a while but I found the Tutorial above. Which said go to your favourite terminal and
gconftool-2 -s /desktop/gnome/url-handlers/spotify/command '/usr/bin/spotify %s' --type String
gconftool-2 -s /desktop/gnome/url-handlers/spotify/enabled --type Boolean true
(well I changed what he had to spotify)
Solution in windows: Add a registry key. Enjoy if your stuck in that OS.