Regarding the web browser issue under Vista, I can't seem to reproduce the issue here. When I run mIRC and open a link from the Help menu, mIRC uses Explorer as expected. If I install Firefox and then open a link, mIRC uses Firefox. If I uninstall and reinstall, and test inbetween, the behaviour is as expected.
I did notice one thing though: if I have Firefox installed and set as the default browser, Explorer still thinks it is the default browser. I check the Explorer "Internet Options/Programs" dialog and it says it is the default. I then check in the Firefox "Main/Options" dialog, and click "Check Now" and it says it is the default. So both browsers think they are the default browser and give no warnings on startup about not being the default.
The only thing I can think of is that this is an issue with Vista's Virtual Store feature, which does not permit an application to modify the main registry if it does not have administrator rights. This may be causing other applications to read incorrect registry information as well.
