[metesky]

Desktop loads and populates, then phoney warning appears and machine locks before you can even twitch.

[mmichaels1970]

Desktop loads and populates, then phoney warning appears and machine locks before you can even twitch.

In Safe mode too?

[KC Burke]

The moment you hit the power button start keying F-8 over and over until the Safe Mode is offered.

[Hillarys Gate Cult]

Good, then my Task Manager suggestion will work. To access hold Control/Alt then only tap on the Delete key, don't hold it or you'll get a restart. Don't wait for Windows to finish loading. I don't know what processes to tell you to shut down as shutting down some will make you have to restart. The name of the piece of malware as a process will possibly look different than real ones ( mixed caps and lower case in the name ). They change it often so it's hard to track down. You only have a few seconds to find and stop it before it launches so this may take a few tries but it does work. If this does kill the malware then do not restart until you get rid of the junk by using earlier suggested programs.

Combofix can do the job but I only recommend it as a last resort as it changes settings you'll spend a good while getting back.