Throw these at the machine in question.
Ccleaner
Malwarebytes Antimalware
Adwcleaner
Hitman Pro
SuperAntispyware
Check browser extensions/addons.
Check for any proxy settings in control panel, internet options, connections, LAN Settings.
Check HOSTS file.
If it is still there after all that.
Run combofix (download from bleepingcomputer.com) (Does'nt work on Windows 8.1 yet.)