Trojan.Kotver!bat Successfully Removed But Firefox Still Redirected

I have Norton Security 22.9.1.12 installed on an old WinXP machine.  Running Firefox 52.1.1 I got this trojan but was able to remove it using the Norton tool posted in several other topics here.

 

My question is this - shortly after starting Firefox, I still get redirected to the malicious website and urged to install the "patch."  I know now to ignore it, but why is the machine still being redirected to this website?  How do I block this website?