Grandkids (probably on U-tube) picked up a vicious malware last night - AV Security Suite. Task Manager was useless, the usual remedies including the current version of Malwarebytes didn't phase it. Popped up an "infected" type message on virtually every screen I accessed, really nasty stuff and virtually killed the machine (running XP).
Using google on another machine, I found this remedy on GeekPolice.net that worked. There may be other ways to remove it but this didn't involve screwing around hunting files and deleting registry entries.
AV Software Suite, as Usual