Try to clean instead of an Downgrade using the following tools:
For each run, restart your computer :
1 - [http://www.bleepingcomputer.com/download/combofix/|ComboFix] ( <= Windows 8 ) Close your Anti-virus before you lunch it !
2 - [https://www.nicolascoolman.com/fr/download/zhpcleaner/|ZHPCleaner]
3 - [https://toolslib.net/downloads/viewdownload/1-adwcleaner/|AdwCleaner]
It will work fine & very fast after that ! :)