Day 2 Keynote Presentation

Great Speaker. Excellent contents
I've spent hours looking for elusive click events in my DOM. This debugger will be life changing!
They should have kept the Spartan name for the browser.
Wonderful session..I've one question..
I've a Win32 app and I would want my application to use spartan for launching links if spartan is set as default browser. Through registry I will currently find out the presence of other browsers (like IE, chrome, etc) and will use reg to identify their install location and launch links. How would I achieve the same if spartan is set as default browser?
which reg key should I look out for?
Thanks!