Have you got the link to the thread you saw saying 'don't remove'?
I did do a bit of searching and found Case Sensitive Search site useful. A tool I was previously unaware of.
Others complain that C:\END is not always detected or removed, but they have eventually removed it by other scanners.
The file contains text "ConduitOk" 9 bytes, but someone else said the file is actually larger.
I wonder if it is hiding an Alternate Data Stream or something?
If it appears gone, hopefully it is.
Check over next few days that it doesn't reappear and that your browsers are not redirecting or behaving oddly
Also check you Browser extensions and add-ons for any you don't recognise.