My daughter clicked on one of those fake ativirus warnings and downloaded a rouge security malware. It was blocking all attempts to remove it.
I had to boot into safe mode and I ran a program called SuperAntiSpyware from a CD. It removed all the malware plus some adware plus the tracking cookies and a trojan backdoor. I rebooted and ran a Windows Defender full scan and found a couple more evil program files. This took hours. I will run a registry cleaner next.
Those fake antivirus warnings are convincing enough except I get them telling me my Windows files are infected when I'm not running Windows.