Sounds like something associated with web browser extensions that add their own default search engines whether its Internet Explorer, Chrome or Firefox.
I would start by resetting each web browser to its default state and disable it from Startup items.
How to **reset Internet Explorer** **settings**
Reset browser settings - Chrome Help - Google Support
**Reset Firefox** – easily fix most problems | **Firefox** Help
Disable Startup items that might associated with this item, look for suspicious items: