windows malicious software remover (MRT) worked for me. You might be able to download it form Microsoft and update it. I like defender also.
The last time I had something like this a few weeks ago it was like described here. It just kept self replicating. Did you try combofix? That is what fixed it for me.
http://www.bleepingcomputer.com/combofix/how-to-use-combofix