My elderly father has been scammed by the guys claiming to be from Microsoft. He had to pay them for some ridiculous antivirus software. Fortunately I found out soon after and managed to immediately get his computer cleaned of potential viruses and scanning software. I also complained to the payment processor (some variant of paypal) and managed to get them to refund the purchase. They still regularly phone him to try to scam him again, but he is now wiser. It is unbelievable what devious tricks people will resort to.