You’re probably already aware of you can clear all your private data from Mozilla Firefox by just going to Tools>Clear Recent History, but have you ever wanted to go a step further? Maybe Firefox is acting up and you don’t feel like re-installing? Maybe you just want to be extra thorough?
Either way, here’s how you delete everything from Firefox: user preferences, bookmarks, and private data like browsing history and cookies. All you need to do is delete one folder.
Note: This tip is not recommended for people to just “try out” as it will DELETE everything associated with Firefox except the program itself. You have been warned.
For Windows XP Users:
Browse to C:>Documents and Settings>(Your User Name)>Application Data (You may need to Show Hidden Folders to see it.)
After you are able to see the Application Data folder, find the folder called “Mozilla” and delete it.
Windows Vista and 7:
First you’ll want to make sure you can see hidden files and folders first by typing “Show Hidden Files” in your Search Box (Located above the Start menu). Once that’s done type “AppData” in your Search Box and press Enter. From here, click Local, find the Mozilla folder and delete it.
There you have it! All of your personal settings, preferences, bookmarks, etc have been deleted and you can start anew!