**Before proceeding backup your bookmarks.
Go to the control panel, click add/remove or programs and features, locate Mozilla Firefox and remove/uninstall.
Delete installation directories C:\Program files\Mozilla Firefox or, on 64-bit Windows, C:\Program Files (x86)\Mozilla Firefox
Enable View Hidden Files and Folders.
Locate folders named "Mozilla" under Documents and Settings or AppData
Open the Registry Editor by pressing the Windows Key + R type regedit and click OK.
Locate;
HKEY_CURRENT_USER
آی-ویدئو