Boot the computer to safe mode with networking and download and install Malwarebytes (freeware version for home users only), update definitions and run in safe mode. Disable other security software whilst you are doing scans.
http://www.computerhope.com/issues/chsafe.htm
http://www.malwarebytes.org/products/malwarebytes_free
Download and run SuperAntiSpyware (Free Edition)