If you're having problems with Mozilla Firefox 31 and want to perform a clean reinstall, remove all traces of the software from your Windows 8 computer. After you uninstall the program from the Control Panel, also remove all its registry entries and application data. Note that editing the registry is dangerous; you can cause programs to malfunction if you delete the wrong keys. Before you start removing Firefox from your PC, back up your bookmarks or your entire profile folder.
Uninstall From the Control Panel
Step 1
Close the Mozilla Firefox program. Press "Windows-X" and select "Control Panel" from the Power User menu. Click the "Uninstall a program" link in the Programs section. If you can't find it, select "Category" from the "View by" list.
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Step 2
Select the "Mozilla Firefox 31" program and click the "Uninstall" button. Click "Next" to continue when the Mozilla Firefox Uninstall wizard displays.
Step 3
Check the "Remove my Firefox personal data and customizations" box to make sure you remove everything. Click "Uninstall" to remove the software from Windows and then click "Finish" to close the uninstall wizard. The process usually takes less than a minute.
Delete Leftover Files and Firefox Data
Step 1
Press "Windows-X" and choose "File Explorer" from the Power User menu to launch the File Explorer. Click the "View" tab and then check the "Hidden items" box in the Show/hide group to display hidden files and folders, such as the AppData folder.
Step 2
Select the system drive, open the "Program Files" folder and locate the Mozilla Firefox folder. Select it, hold "Shift" and press "Delete." Click "Yes" to confirm and permanently delete all the leftover files. If you installed Mozilla on a different drive, locate its folder and delete it using the same procedure.
Step 3
Open the "C:\Users\Your_Username\AppData" folder. Open the "Local," "LocalLow" and "Roaming" folders and delete the "Mozilla" folder from each one to delete the program's leftover data.
Remove Firefox From the Registry
Step 1
Press "Windows-R" to open the Run dialog, type "regedit" into the Run box and press "Enter" to open the Registry Editor. The Windows Registry is a database that stores the configuration settings of all Windows programs installed on your computer.
Step 2
Open the "HKEY_LOCAL_MACHINE\Software" key and locate the "Mozilla" key. Select it, press "Delete" and then click "Yes" to confirm and delete the Firefox keys from the Registry.
Step 3
Close the Registry Editor window. Don't delete any other keys or values unless you know what you're doing. Tampering with the Windows Registry can cause apps to malfunction and even crash the entire operating system.