Did you useWindows Defender Offline as per Borg post #2
Two other things.
1. Removing it using Safe Mode.
2. Internet Options/Connection/Lan and make sure proxy is not checked.
I just went through something like this and many times a anti malware don't find it because it's not considered malware. It can also be a add on in your browser. Something like, (Price watcher, coupon saver) or the likes. Completely remove all browsers except I.E. Then set I.I. to default. Nothing added what so ever. If your okay you can add more browser of your choice.