The development team at Firefox is listening - a new release candidate (version 1.0.3) has been posted that attempts to address the mess created when installing a new version of the browser. This release also improves the manual installation of plug-ins. I think I'll wait for the release version this time (it should be RSN - real soon now) and see how it works but if you're feeling adventurous, give it a try and let them know what you think. Here are the notes from the project site:

"The first thing that we've fixed that we need your help testing is the Windows "Add or Remove Programs" bug that caused a doubling up of uninstall entries. This new build should behave correctly, in that if you install it on top of an older release, it will replace that older release's entry rather than add a new one.

The second area that we could use your help testing is manual installation of plugins. If you can find sites that offer plugins which we don't support with the Plugin Finder Service, then clicking on the puzzle piece or the "Install missing plugins" button in the information bar should result in a Plugin Finder Service dialog with a "Manual Installation" button which should take you to the web page for manual installation. If you can find cases where that doesn't work, please let me know."

Download the latest build and check other testers' coments here.