In Windows I have registered my own handler for an external protocol in the registry. When I click the link in Firefox or Thunderbird I'm shown the "Launch Application" dialog in which I should choose an application for handling the protocol, but the program I've registered as default handler is not listed as an alternative i.e. the only entry in the list is "Choose an Application" Observations: * I'm never shown a message stating that the protocol is unknown, i.e. the registry entry is found * The links works as expected in IE. * If I register the application to another of my programs I get an entry in the dialog for some programs, but not for others. I haven't found any difference in the programs that would cause them to be listed or not. Icons are never shown in the dialog, although defined in the protocols registry settings. * If I put an illegal program path in the registry I get an entry in the dialog!? * The same problem occurs regardless of the protocol identifier I choose * Behaviour is the same regardless if the protocol is registered under HKEY_CLASSES_ROOT or HKEY_CURRENT_USER\Software\Classes * If I change "network.protocol-handler.warn-external-default" in about:config to false my program is successfully launched when clicking the link * Currently running on Windows 7 Starter Edition, but the same happens on other versions of Windows 7 and Windows Vista 64-bit as well