When I get those calls, and they tell me that my MS Windows machine is corrupted / has a virus / etc.... I tell them, that is interesting, I only run Linux.
At which point they usually hang up.
If I want to play with them, I will ask them “Which one?” Is it the downstairs, or loft or the two laptops? And after a while I start to use my tech background to really mess with them.
I work in an enterprise so I ask which one of the 1000 machines are they talking about...click!