Redirecting Problem W/ Firefox

I'm running Windows 10 and decided to start a new thread because I didn't see a thread which addressed Win10. I downloaded a bad file which is causing issues w/ my Firefox homepage. It is continually being re-set to Bing. I can re-set it during a session, but when I close Firefox and restart, it reverts back to Bing.
I've ran Malwarebytes, MSDefender, AdvancedSystemCareV9, and a couple other virus/malware removal tools.
I even tried uninstalling Firefox and re-installing it w/ no success. During the uninstall, I manually deleted Mizolla folders. But there were a couple folders which I could not delete. (I am the administrator)
I've read several threads which referenced Win7 and tried a couple of the tools referenced in those threads. I thought in Win7 there was a system setting which prevented the homepage from being reset. But I can't find such setting in Win10.
I can provide more info, but I don't know what at this time.
Any suggestions will be appreciated.

 

Yes, you're correct. This was not malware. It was caused by me installing AdvancedSystemCare v9. It has a setting for the homepage burried deep down inside it. For some reason on the PC w/ Win 10, it got set to Bing.
THANKS very much for your reply. I guess I just need a nudge to dig deeper. This site is a Great source of info. Keep up the Good work.