I helped do some Spring Autumn cleaning on a PC today. (To protect the innocent, I won't say whose, just that it wasn't mine.) Thanks to Robert's help (it was he who pointed me in the right direction after reading about the symptoms), we used MalwareBytes and let it run. The program removed all sorts of rubbish, including:
Rogue.Antivirus Rogue.Antivirus2008 Rogue.AntivirusXP Rogue.AntivirusXP2008 Rogue.Multiple Rootkit.Agent Trojan.Agent Trojan.BHO Trojan.Downloader Trojan.FakeAlert
All this on a PC that is protected by an up-to-date Mcaffee Virusscan. Sigh.