BTW, implementing a backup plan can also save you from the occasional slip up, which happened to me recently. I was uninstalling some old, outdated programs, and didn't even think twice removing old versions of Firefox v12 and Thunderbird from my desktop. I had monitored these installs using an uninstall app, but didn't realize that the app also monitored all updates since that install. So when I went to uninstall Firefox v12, the app also uninstalled the current version v33 including my profile folders.
FYI, Firefox profile folder contains all browser add-on extensions, preferences, bookmarks and passwords. Same with Thunderbird, which contains locally stored emails, account settings and email passwords. :S
As I mentioned, my data files get auto backed up twice daily, including Firefox and Thunderbird profile folders, which are actually stored encrypted on my backup drive. So just a matter of reinstalling both programs and restoring the backed up profile folders. In the end, took just 15 minutes to get both Firefox and Thunderbird back to what it was, for the most part, before they were inadvertently uninstalled.