Firefox not really default browser in Vista

I installed twhirl, to give it a twirl with twitter.

First issue was that URLs opened in Internet Explorer, instead of in Firefox. A bit searching lead me to throk.net for a possible solution, but Mozilla Firefox doesn’t show up under Set Program Access and Computer Defaults. It was mentioned that Flock doesn’t show up either, but Firefox 3 does.

Next try brought me to CNET’s Forums, where it was pointed out that IE still holds some file associations (*.url for one). Before I tried to mess around with that, I tried the suggestion of one LinuxDude; executing the following command from the Run dialog (Win key + R): firefox.exe -silent -setDefaultBrowser

This worked, but I can’t see any changes in Default Programs. I haven’t restarted yet, though.