Had one last year, from "Microsoft", I had a spare moment or two so played along. Acting as dumb and computer illiterate as possible. You could hear the excitement in the guys voice when he thought he'd got a right sucker.
Usual you have a virus, followed by a lame attempt to get you to look for some odd/suspicious looking, but perfectly innocent standard file via explorer.
"If you could just press the Windows key for me", "Er, what's the Windows key? is it one of those with a funny little picture on it?" And so it went on. "Can you click on the start button?". Me, "oh no, I can't find one of those, is it on the key board, or do you mean the power button?"
Increasingly exasperated description of where to find it, me, "oh no! It's missing, this virus is really bad isn't it?"
So then he starts getting me to download the "Microsoft" remote support software. "It won't install, I tell him, keeps popping up a talky boxy thingy on the screen"
"It says wrong version and lots and lots of numbers"
"Oh" he said, "what version of Windows are you on", "Er I'm not sure, but it says OS X if I click on the about button"
Silence, very annoyed voice, "can you tell me what make of PC it is please". Me, "Oh I though you said you could tell, er, I'm not sure. I can't see a brand, it's silver though"
"Oh, there's some writing under the screen, it says MacBook Pro, is that the brand, er hello, hello, are you still there...."
But he'd gone, and I had the pleasure of knowing that for the length of my coffee break at least, he hadn't been hoodwinking some poor sucker.