That's the trouble with these damned things - you can't get rid of them.
If you want to completely start again with a 'clean' Firefox, after you have uninstalled it, you can remove all of the plugins and saved settings by deleting the Profile folder, which is hidden in C:\Documents and Settings\[username]\Application Data\Mozilla\Firefox\Profiles. In there you will find a folder named with random letters and numbers. This is your Profile folder. You may have to reveal hidden folders to see this, by going to Tools > Folder Options > View > then scroll down to Hidden files and folders and tick the button to Show. Be aware that deleting the Profile folder will completely remove all of your saved settings, including bookmarks, saved passwords etc, but these can be Imported from IE again when you re-install FF. Alternatively, you can open the folder and make a backup copy elsewhere of the Bookmarks.htm, then you can just copy it back into the new folder which will be created when you re-install.
Also, go to C:\Program Files and delete the Firefox folder from in there. Hopefully, HotFix will then not reappear if you re-install FF. You could, of course, leave things as they are, if you have found a way to hide the HotFix toolbar - but you'll always know it's there, and there might be a chance that it could conflict with the Email Notifier, but you won't know that until you install it.