I've ceased recommending Malwarebytes Anti-Malware because
(a) you're now forced into taking a free trial of the Premium version ; and
(b) that version seems to slow some computers down.
However Malwarebytes bought up a rival product which, because it's now out of the same stable as Malwarebytes Anti-Malware, is every bit as good as it but doesn't get you involved in any trial periods. It's called AdwCleaner:
https://www.malwarebytes.com/adwcleaner/
(If you'd still prefer to go with Malwarebytes Anti-Malware though, use the 'free trial' link here. If you don't pay to subscribe it will eventually revert to the free product:
https://www.malwarebytes.com/premium/ )