In IE, I can easily disable Flash, and enable it on the rare occasion it performs useful task. But I cannot fix the javascript "install silverlight" pop-ups on all msdn and related websites. Yes, Firefox will do the trick! Microsoft, see how your hostile modal dialogs drive people away from IE!
I did a google search and found many people angry about this. It seems like a sleazy way to increase installation statistics. Many people have flash installed, but the vast majority of flash downloads are blocked either by corporate firewalls, or client software. The same will happen to silverlight. Installation statistics are meaningless.