I take it you don't know how to clean out the registry, then? It's a simple task. I'd say download and install RegCleaner, click on Software and check off anything that says Firefox or Mozilla and click Remove Selected. Do the same in the Startup List and Uninstall Menu. Once that is done, you can exit and reboot. Do that AFTER you've uninstalled what you have now. It might work, and I do believe it may be better for those who prefer not to go directly into the registry sections and editing things manually.