Win Erx03 pops up constantly

This has just started. Almost impossible to close the page except by using Task Manager but then it pops up again. It is not in the download list in control panel nor in my search providers. I've changed my default homepage. I've done a search in the Registry to no avail so it must be residing somewhere.
All help gratefully received.
P.S. I would send likes as I believe people who help should be rewarded somehow but I do not belong to any social media so I'll send a personal like here.