Mozilla Firefox stores your browser settings, bookmarks, add-ons, passwords, cookies, and themes in a "Profile" to make it easier to manage them. These profiles can be changed, deleted or renamed using the Profile Manager. A new profile is useful, especially if you are having issues with your browser, because it allows the browser to run without extensions, themes, and customized settings. Changing your Mozilla Firefox profile is a quick and easy process.
Close Mozilla Firefox if you have it running.
Click the Windows "Start" button and click "Run" or "Start," then "Search" (Windows Vista users).
Type "firefox.exe -profilemanager" (without quotes) and press "Enter" to open the Firefox Profile Window.
Click "Delete Profile" to remove the current profile. Then click "Create Profile." The creation wizard will automatically open.
Click "Next" on the creation wizard. Type a name for your profile and select the folder to save the profile to.
Click "Finish" and click "Start Firefox" to launch Mozilla Firefox and complete the profile change process.