The Microsoft Internet Explorer team has fixed, albeit a bit late, the IE 8 set-up to not trick or confuse people into making IE 8 their default browser.
The problem was that most Windows users were getting a prompt from Windows Update to get the new IE 8 and that new version was causing a lot of people to accidentally replace their current default browser with IE 8 because "express settings" which most people were opting for looked like the best way to complete the setup, included the action of undoing the user's default browser choice.
Updating your Windows software, even if you don't use it regularly, is a good thing because some "broken" Windows apps will call programs like IE directly instead of the default browser. Having old and insecure versions of IE on your system is actually dangerous so I'm glad people are upgrading.
But, upgrading non-default and rarely used software shouldn't have the side-effect of undoing user choice. Microsoft's update process was doing just that. Microsoft is taking a good step to remedy this and that's a good thing.
Maybe more important than the Windows Update for XP and Vista users is that Microsoft has indicated that this will also be fixed for people upgrading their OS to Windows 7. Until now, it had appeared that people upgrading to Windows 7 were also going to be misled into accidentally replacing their current default browser with IE 8.
Microsoft is a convicted monopolist in the US and is facing serious anti-competition allegations in the EU and because of that they have to be a lot more careful about using their status as OS provider to undo user choice like this. They're a bit late on this for the IE 8 roll-out, which has been going on for several months now, but I'm glad they're getting it fixed before Windows 7.