I had this a while ago
I had this a while ago and thought it quite dodgy at the time. I was phoned and they said they were Microsoft support personnel and that they had been given reports that my machine was infected and sending viruses to other machines and they could help me fix it. I strung them along for fifteen minutes trying to act like a moron and getting web addresses wrong just to piss them off, then acted like my system was win95. The guy got so frustrated on the other end he ended up just putting the phone down on me. I've had about 3-4 of these calls in the last year or so.
Biting the hand that feeds IT
