Can you please make sure that everything related is uninstalled in "Add or remove programs" in Windows?
And that there is no related extension in Mozilla Firefox?
1. Type about:config in the address bar and press Enter.
2. Press the I'll be careful, I promise! button.
3. Type search in the Search text box.
4. Right-click the browser.search.defaultenginename and select Reset from the context menu.
5. Type keyword in the Search text box.
6. Right-click the keyword.URL item and select Reset from the context menu
What is the current situation?