Click on xmpp:// URI to open existing Spark instance

When I click on a link xmpp://xxxx I want the Shell open command that runs spark.exe to use an existing instance if Spark is already running. Does Spark support this - if not can it be easily implemented?

I read the other posts about spark.ini, starter.ini but can’t find any of those anywhere (Win7). I have tried setting the registry to run “starter.exe Spark.exe %1” and that seems to work at least in the cases I tried, but is that how it should be done?