Try looking for it as a program that may be removed from windows control panel. I have not come across this myself but I note there is a thread apparently relating to this problem [https://support.mozilla.com/en-US/questions/770771] ''"How can I uninstall the Freeze.com NetAssistant add-on please? It will not uninstall in Safe-mode, it's not in \Profiles\i2szmemp.default\extensions and I can't find on the C:\ drive to remove. Can anyone help please?"'' Note in that thread there is a mention of a potential removal tool, being reported as a trojan, so if you do download any removal tools to help you, it may be wise to have them security scanned before you consider employing them.