Sidebar weather not updating
[thread 2007-03-25] Although all add-ons presumably were restored at addons on 2007-03-26 that is not actually the case so if still missing you can load from ftp://ftp.mozilla.org/pub/mozilla.org/extensions If you have an extension installed you can find what the author supplied as homepage via Tools, Add-ons ("Ctrl Shift A")_, and right click on the addon.
Do not install an extension you are suspicious of, most extensions you will ever use are from the one of the four locations listed earlier.
Multiple profiles: is one way of essentially turning off all extensions so you can test w/o or with only one extension – Firefox Help: How To Manage Profiles, Multiple profiles and profile management is an advanced feature, mainly intended for developers.
Unless you are an extension developer or an advanced user, you should probably not be trying to use multiple profiles.
Old versions: The problem often turns out to be something else, but if you want to restore an older version, you will probably find it in your downloads; otherwise, start at ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/ then choose version, platform (win32), language (en-US).
Don't worry too much about the type, you will see how they group from the above examples. To help create a Launchy entry use file search to find the directory, if you have a problem it could be you have more than one, or you can't simply use something like as you could from the Run program dialog.